Starkey Research & Clinical Blog

Tinnitus Treatment through Sound Therapy

Henry, J., Frederick, M., Sell, S., Griest, S. & Abrams, H. (2014). Validation of a novel combination hearing aid and tinnitus therapy device. Ear and Hearing, e-published ahead of print, September 2014.

This editorial discusses the clinical implications of an independent research study and does not represent the opinions of the original authors.

Background

Most tinnitus management programs include a combination of counseling and sound therapy (Jastreboff, 1990; Jastreboff & Hazell, 2004). The goals of sound therapy for tinnitus treatment include achieving immediate relief as well as facilitating long-term habituation to the tinnitus (Vernon, 1988; Jastreboff & Hazell, 1998). Many sound generators or tinnitus masking devices offer only basic amplification features because they were intended primarily for tinnitus treatment through sound therapy. Current combination devices with advanced digital signal processing can provide improved audibility and comfort in addition to offering noise stimuli (i.e., sound therapy) for tinnitus management. Some estimates report that up to 90% of patients with tinnitus may benefit from amplification (Johnson, 1998; Schechter et al., 2002) so combination hearing aid / sound therapy devices are a valuable tool for tinnitus treatment and hearing loss remediation.

Most scientific studies support the potential benefit of hearing aids for tinnitus management. In a recent literature review, Shekhawat et al. (2013) reported that 17 of 18 research studies included the use of hearing aids in tinnitus treatment, but they highlighted the absence of randomized control trials with hearing aids that include sound therapy options. Parazzini et al. (2010) found that open-fit hearing aids were as effective as sound generator-only devices for use in tinnitus therapy, but they did not investigate combination devices. A primary goal of therapy is to reduce tinnitus awareness, so combination devices could be particularly beneficial because they employ masking stimuli as well as amplified environmental sound that may effectively draw attention away from the tinnitus. Though this proposition has merit, it has not yet been supported by scientific evidence. To this end, Henry and his colleagues prepared a randomized, controlled trial to investigate the benefit of hearing aids versus combination devices for tinnitus management.

Methods and Findings

Thirty participants with mild-to-moderately severe, symmetrical, sensorineural hearing loss were recruited for this study. All had clinically significant tinnitus according to Section A of the Tinnitus and Hearing Survey (Henry et al., 2010a, 2012). At the first session, subjects completed audiometry, medical and tinnitus screening and responded to 3 questionnaires: the Tinnitus Functional Index (TFI; Meikle et al., 2012), the Hearing Handicap Inventory for the Elderly (HHIE; Ventry & Weinstein, 1982) and a general tinnitus survey.  The TFI evaluates the negative impact of tinnitus and measures changes in tinnitus impact after treatment. TFI scores range from 0 to 100, with higher scores indicating more severe problems. Scores of at least 25 are considered significant and a 13-point difference from one test administration to another is considered a significant change. The HHIE evaluates the social and emotional effects of hearing loss and higher scores indicate more social and emotional impact. In this study, the HHIE was administered face-to-face, so a change of 19 points from one session to another was considered significant.

At the second session, participants were fitted with receiver-in-canal (RIC) hearing instruments that included the Multiflex adjustable sound-generator. Most subjects used manufacturer’s silicone domes, but two required custom fitted acrylic earmolds. Hearing aids were programmed to NAL-NL2 targets, verified with real-ear measures and adjusted according for sound quality and comfort. Following hearing aid fitting, all participants received general tinnitus counseling derived from Progressive Tinnitus Management: Counseling Guide (Henry et al., 2010b). Following counseling, the experimental group had the tinnitus sound therapy in their hearing aids adjusted according to their individual preferences to obtain immediate relief from their tinnitus, while the control group was prescribed hearing aids without the tinnitus sound therapy.  The default settings for the modulated noise stimuli were based on the individual’s audiogram, but could be adjusted in 16 channels and subjects could select a slow, medium or fast modulation rate.

Approximately 3 to 4 months after the initial fitting appointment, participants returned to complete an exit interview. They were asked about their general impressions of hearing aids and experience of tinnitus relief and completed the TFI and HHIE inventories two more times; once to indicate their responses when they were using their hearing aids and again to indicate their responses when they were not using their hearing aids.

TFI and HHIE scores were obtained 3 times each: at the initial visit prior to hearing aid fitting and at the 3-month session, for responses referring to experiences with the hearing aids and without. The initial average TFI score for the overall subject group was 58.3. At the 3-month session, the average TFI scores were 22.2 (with hearing aids) and 44.8 (without hearing aids). Though the change in score for the with-hearing-aid condition was much larger, the reductions in score were significant for both conditions. For the control group, the initial score was 60.5 and at 3 months the average scores were 27.6 (with hearing aids) and 44.3 (without hearing aids). Again, both reductions were significant, though the effect size for the with-hearing-aids condition was much larger. For the experimental group, the initial average score was 56.1. At the 3-month session, the average scores were 16.8 (with hearing aids) and 45.3 (without hearing aids). The score reduction was significant for the with-hearing-aids condition but not for the without-hearing-aids condition. These outcomes indicate that both groups, regardless of whether the sound therapy was used or not, responded better to TFI questions with respect to when they were wearing the hearing aids versus when they were not.  There was no significant difference between the TFI score reductions for the control versus experimental groups, though the experimental group had a larger score reduction by about 6 points.

At the 3-month session, the average HHIE scores were 23.6 (with hearing aids) and 47.5 (without hearing aids). The score reduction was significant for the with-hearing-aid condition but was not for the without-hearing-aid condition. For the control group, the initial score was 55.3 and at 3 months the average scores were 26.9 (with hearing aids) and 47.5 (without hearing aids). For the experimental group, the initial average HHIE score was 49.3 and at the 3-month session the average scores were 20 (with hearing aids) and 47.5 (without hearing aids). Again, for both the control and experimental groups, the score reduction was significant for the with-hearing-aid condition but was not for the without-hearing-aid condition.  There was a significant main effect between initial scores and 3-month scores for the with-hearing-aid condition but not for the without-hearing-aid condition. There was also a significant difference between the two conditions at the 3-month session; the with-hearing-aid scores were significantly lower than without-hearing-aid scores.

Discussion

The findings of Henry and colleagues indicate that hearing aid use significantly reduces the negative effects of tinnitus, regardless of the presence or absence of sound therapy. Though there was not a significant difference between the control and experimental groups, the group using sound therapy had a larger reduction in TFI score than the group that used amplification alone. This difference approached but did not reach significance and the authors posit that perhaps with a larger subject group this difference would have been significant. HHIE results suggest that hearing aid benefit was not hampered by the use of sound therapy.

From a clinical perspective, several factors should be considered when fitting combination devices. The TFI is a good way to determine candidacy for combination devices, but a few key questions in the patient history can be helpful. We ask patients how they would rate their tinnitus and if it disrupts concentration, distracts or upsets them. It is also informative to ask if their tinnitus keeps them awake at night, though this concern is not directly addressed by the use of a combination device. Even a question about how motivated they are to seek treatment, such as the one employed in this study, can be indicative of candidacy.

After candidacy is established, there are still several factors to consider. Discussion of the individual’s tinnitus characteristics might help indicate which type of noise is most likely to be effective. Shaping the noise by frequency and intensity can help to achieve relief, while avoiding annoyance that may come with continued use. Clinicians should also discuss whether patients would like to use the noise constantly, in their main hearing aid program, or have it allocated to an alternate program for use as needed. We have found that most people prefer to have a “masking program” that they can use on occasion when their tinnitus is disruptive or annoying. For many people, this is in quiet conditions when they must concentrate on reading or quiet work. Follow-up consultations are critical to determine if the approach is working. Some individuals prefer to modify the characteristics of their sound therapy at later visits, either increasing or decreasing the intensity or shaping the frequency bands. The TFI is useful as a follow-up measure, but it should probably be administered after a few months of use, to make sure that programming adjustments are worked out before treatment efficacy is assessed.

References

Bock, K. & Abrams, H. (2013). An evaluation of the efficacy of a remotely driven auditory training program. Biennial NCRAR International Conference: Beyond the Audiology Clinic: Innovations and Possibilities of Connected Health. Portland, OR.

Coles, R. (2000). Medicolegal issues. In R.S. Tyler (Ed.). Tinnitus Handbook (pp. 399-417). San Diego: Singular Publishing Group.

Henry, J., Frederick, M., Sell, S., Griest, S. & Abrams, H. (2014). Validation of a novel combination hearing aid and tinnitus therapy device. Ear and Hearing, e-published ahead of print, September 2014.

Henry, J., Zaugg, T. & Myers, P. (2010a). Progressive Tinnitus Management: Clinical Handbook for Audiologists. San Diego, CA: Plural Publishing.

Henry, J., Zaugg, T. & Myers, P. (2010b).  Progressive Tinnitus Management: Counseling Guide. San Diego, CA: Plural Publishing.

Henry, J., Zaugg, T. & Myers, P. (2012). Pilot study to develop telehealth tinnitus management for persons with and without traumatic brain injury. Journal of Rehabilitation Research Developments 49, 1025-1042.

Hoffman, H. & Reed, G. (2004). Epidemiology of tinnitus. In J.B. Snow (Ed.). Tinnitus: Theory and Management (pp. 16-41). Lewiston, NY: BC Decker, Inc.

Humes, L., Wilson, D. & Barlow, N. (2002). Longitudinal changes in hearing aid satisfaction and usage in the elderly over a period of one or two years after hearing aid delivery. Ear and Hearing 23, 428-438.

Jastreboff, P. (1990). Phantom auditory perception (tinnitus): Mechanisms of generation and perception. Neuroscience Research 8, 221-254.

Jastreboff, P.  & Hazell, J. (1998). Treatment of tinnitus based on a neurophysiological model. In J.A. Vernon (Ed.). Tinnitus Treatment and Relief (pp. 201-217). Needham Heights: Allyn & Bacon.

Jastreboff, P. & Hazell, J. (2004). Tinnitus Retraining Therapy: Implementing the Neurophysiological Model. Cambridge University Press.

Johnson, R. (1998). The masking of tinnitus. In J.A. Vernon (Ed.). Tinnitus Treatment and Relief (pp. 164-186). Needham Heights: Allyn & Bacon.

Meikle, M. & Taylor-Walsh, E. (2012). Characteristics of tinnitus and related observations in over 1800 tinnitus patients. Proceedings of the Second International Tinnitus Seminar. New York 1983. Ashford, Kent, Invicta Press. Journal of Laryngology and Otology Suppl. 9, 17-21.

Mulrow, C., Tuley, M. & Aguilar, C. (1992). Sustained benefits of hearing aids. Journal of Speech and Hearing Research 35, 1402-1405.

Parazzini, M., Del Bo, L., Jastreboff, M., Tognola, G. & Ravazzani, P. (2010). Open ear hearing aids in tinnitus therapy: An efficacy comparison with sound generators. International Journal of Audiology 2011 Early Online, 1-6.

Schechter, M., Henry, J. & Zaugg, T. (2002). Selection of ear level devices for two different methods of tinnitus treatment. VIIth International Tinnitus Seminar Proceedings. R. Patuzzi. Perth, Physiology Department, University of Western Australia, p. 13.

Shekhawat, G., Searchfield, G. & Stinear, C. (2013). Role of hearing aids in tinnitus intervention: A scoping review. Journal of the American Academy of Audiology 24, 747-762.

Surr, R., Montgomery, A. & Mueller, H. (1985). Effect of amplification on tinnitus among new hearing aid users. Ear and Hearing 6, 71-75.

Ventry, I. & Weinstein, B. (1982). The hearing handicap inventory for the elderly: A new tool. Ear and Hearing 3, 128-134.

Vernon, J. (1988). Current use of masking for the relief of tinnitus. In M. Kitahara (Ed.). Tinnitus. Pathophysiology and Management (pp. 96-106). Tokyo: Igaku-Shoin.

Vernon, J. (1992).  Tinnitus: causes, evaluation and treatment. In G.M. English (Ed.). Otolaryngology (Revised Edition), pp. 1-25. Philadelphia: J.B. Lippincott.

On the Prevalence of Cochlear Dead Regions

Pepler, A., Munro, K., Lewis, K. & Kluk, K. (2014). Prevalence of Cochlear Dead Regions in New Referrals and Existing Adult Hearing Aid Users. Ear and Hearing 20(10), 1-11.

This editorial discusses the clinical implications of an independent research study and does not represent the opinions of the original authors.

Cochlear dead regions are areas in which, due to inner hair cell and/or nerve damage, responses to acoustic stimuli occur not at the area of peak basilar membrane stimulation but instead occur at adjacent regions in the cochlea. Professor Brian Moore defined dead regions as a total loss of inner hair cell function across a limited region of the basilar membrane (Moore, et al., 1999b). This hair cell loss does not result in an inability to perceive sound at a given frequency range, rather the sound is perceived via off-place or off-frequency listening, a spread of excitation to adjacent regions in the cochlea where inner hair cells are still functioning (Moore, 2004).  Because the response is spread across a broad tonotopic area, individuals with cochlear dead regions may perceive pure tones as “clicks”, “buzzes” or “whooshes”.

Cochlear dead regions are identified and measured by a variety of masking techniques. The most accurate method is the calculation of psychophysical tuning curves (PTCs), originally developed to measure frequency selectivity (Moore & Alcantara 2001). A PTC plots the level required to mask a stimulus frequency as a function of the masker frequency. For a normally hearing ear, the PTC peak will align with the point at which the stimulus can be masked by the lowest level masker.  In ears with dead regions, the tip of the PTC is shifted off of the signal frequency to indicate that the signal is being detected in an adjacent region. Though PTCs are an effective method of identifying and delineating the edges of cochlear dead regions, they are time consuming and ill-suited to clinical use.

The test used most frequently for clinical identification of cochlear dead regions is the Threshold Equalizing Test (TEN; Moore et al., 2000; 2004). The TEN test was developed with the idea that tones detected by off-frequency listening, in ears with dead regions, should be easier to mask with broadband noise than they would in ears without dead regions. With the TEN (HL) test, masked thresholds are measured across the range of 500Hz to 4000Hz, allowing the approximate identification of a cochlear dead region.

There are currently no standards for clinical management of cochlear dead regions. Some reports suggest that affect speech, pitch, loudness perception, and general sound quality (Vickers et al., 2001; Baer et al., 2002; Mackersie et al., 2004; Huss et al., 2005a; 2005b). Some researchers have specified amplification characteristics to be used with patients with diagnosed dead regions, but there is no consensus and different studies have arrived at conflicting recommendations. While some recommend limiting amplification to a range up to 1.7 times the edge frequency of the dead region (Vickers et al., 2001; Baer et al., 2002), others advise the use of prescribed settings and recommend against limiting high frequency amplification (Cox et al., 2012; see link for a review).  Because of these conflicting recommendations, it remains unclear how clinicians should modify their treatment plans, if at all, for hearing aid patients with dead regions.

Previous research on the prevalence of dead regions has reported widely varying results, possibly due to differences in test methodology or subject characteristics. In a study of hearing aid candidates, Cox et al. (2011) reported a dead region prevalence of 31%, but their strict inclusion criteria likely missed individuals with milder hearing losses, so their prevalence estimate may be different from that of hearing aid candidates at large. Vinay and Moore (2007) reported higher prevalence of 57% in a study that did include individuals with thresholds down to 15dB HL at some frequencies, but the median hearing loss of their subjects was higher than that of the Cox et al. study, which likely impacted the higher prevalence estimate in their subject group.

In the study being reviewed, Pepler and her colleagues aimed to determine how prevalent cochlear dead regions are among a population of individuals who have or are being assessed for hearing aids. Because dead regions become more likely as hearing loss increases, and established hearing aid patients are more likely to have greater degrees of hearing loss, they also investigated whether established hearing aid patients would be more likely to have dead regions than newly referred individuals.  Finally, they studied whether age, gender, hearing thresholds or slope of hearing loss could predict the presence of cochlear dead regions.

The researchers gathered data from a group of 376 patients selected from the database of a hospital audiology clinic in Manchester, UK. Of the original group, 343 individuals met inclusion criteria; 193 were new referrals and 150 were established patients and experienced hearing aid users.  Of the new referrals, 161 individuals were offered and accepted hearing aids, 16 were offered and declined hearing aids and 16 were not offered hearing aids because their losses were of mild degree.  The 161 individuals who were fitted with new hearing aids were referred to as “new” hearing aid users for the purposes of the study. All subjects had normal middle ear function and otoscopic examinations and on average had moderate sensorineural hearing losses.

When reported as a proportion of the total subjects in the study, Pepler and her colleagues found dead region prevalence of 36%.  When reported as the proportion of ears with dead regions, the prevalence was 26% indicating that some subjects had dead regions in one ear only. Follow-up analysis on 64 patients with unilateral dead regions revealed that the ears with dead regions had significantly greater audiometric thresholds than the ears without dead regions. Only 3% of study participants had dead regions extending across at three or more consecutive test frequencies. Ears with contiguous dead regions had greater hearing loss than those without.  Among new hearing aid users, 33% had dead regions while the prevalence was 43% among experienced hearing aid users. On average, the experienced hearing aid users had poorer audiometric thresholds on average than new users.

Pepler and colleagues excluded hearing losses above 85dB HL because effective TEN masking could not be achieved. Therefore, dead regions were most common in hearing losses from 50 to 85dB HL, though a few were measured below that range. There were no measurable dead regions for hearing thresholds below 40dB HL. Ears with greater audiometric slopes were more likely to have dead regions, but further analysis revealed that only 4 kHz thresholds had a significant predictive contribution and the slopes of high-frequency hearing loss only predicted dead regions because of the increased degree of hearing loss at 4 kHz.

Demographically, more men than women had dead regions in at least one ear, but their audiometric configurations were different: women had poorer low frequency thresholds whereas men had poorer high frequency thresholds. It appears that the gender effect actually due to the difference in audiometric configuration, specifically the men’s poorer high frequency thresholds. A similar result was reported for the analysis of age effects. Older subjects had a higher prevalence of dead regions but also had significantly poorer hearing thresholds.  Though poorer hearing thresholds at 4kHz did slightly increase the likelihood of dead regions, regression analysis of the variables of age, gender and hearing thresholds found that none of these factors were significant predictors.

Pepler et al’s prevalence data agree with the 31% reported by Cox et al (2012), but are lower than that reported by Vinay and Moore (2007), possibly because the subjects in the latter study had greater average hearing loss than those in the other studies.  But when Pepler and her colleagues used similar inclusion criteria to the Cox study, they found a prevalence of 59%, much higher than the report by Cox and her colleagues and likely due to the exclusion of subjects with normal low frequency hearing in the Cox study. The authors proposed that Cox’s exclusion of subjects with normal low frequency thresholds could have reduced the overall prevalence by increasing the proportion of subjects with metabolic presbyacusis and eliminating some subjects with sensory presbyacusis—sensory presbyacusis is often associated with steeply sloping hearing loss and involves atrophy of cochlear structures (Shuknecht, 1964).

 In summary:

The study reported here shows that roughly a third of established and newly referred hearing aid patients are likely to have at least one cochlear dead region, in at least one ear. A very low proportion (3% reported here) of individuals are likely to have dead regions spanning multiple octaves. The only factor that predicted the presence of dead regions was hearing threshold at 4 kHz.

On the lack of clinical guidance:

As more information is gained about prevalence and risk factors, what remains missing are clinical guidelines for management of hearing aid users with diagnosed high-frequency dead regions. Conflicting recommendations have been proposed for either limiting high frequency amplification or preserving high frequency amplification and working within prescribed targets. The data available today suggest that prevalence of contiguous multi-octave dead regions is very low and a further subset of hearing aid users with contiguous dead regions experience any negative effects of high-frequency amplification. With consideration to these observations, it seems prudent that the prescription of high-frequency gain should adhere to the prescribed targets for all patients at the initial fitting. Any reduction to high-frequency gains should be managed as a result of subjective feedback from the patient after they have completed a trial period with their hearing aids.

On frequency lowering and dead regions:

Some clarity is required regarding the role of frequency lowering and the treatment of cochlear dead regions. Because acoustic information in speech extends out to 10 kHz and because most hearing aid frequency responses roll off significantly after 4-5 kHz, the mild prescription of frequency lowering can be beneficial to many hearing aid users. It must be noted that the benefits of this technology arise largely from the acoustic limitations of the device and not the presence or absence of a cochlear dead region. There are presently no recommendations for the selection of frequency lowering parameters in cases of cochlear dead regions. In the absence of these recommendations, the best practice for the prescription of frequency lowering would follow the same guidelines as any other patient with hearing loss; validation and verification should be performed to document benefit with the algorithm and identify appropriate selection of algorithm parameters.

On the low-frequency dead region: 

The effects of low-frequency dead regions are not well studied and may have more significant impact on hearing aid performance.  Hornsby (2011) reported potential negative effects of low frequency amplification if it extends into the range of low-frequency dead regions (Vinay et al., 2007; 2008). In some cases performance decrements reached 30%, so the authors recommended using low-frequency gain limits of 0.57 times the low-frequency edge of the dead region in order to preserve speech recognition ability. Though dead regions are less common in the low frequencies than in the high frequencies, more study on this topic is needed to determine clinical testing and treatment implications.

References

Baer, T., Moore, B. C. and Kluk, K. (2002). Effects of low pass filtering on the intelligibility of speech in noise for people with and without dead regions at high frequencies. Journal of the Acoustical Society of America 112(3 Pt 1), 1133-44.

Cox, R., Alexander, G., Johnson, J., Rivera, I. (2011). Cochlear dead regions in typical hearing aid candidates: Prevalence and implications for use of high-frequency speech cues. Ear and Hearing 32(3), 339 – 348.

Cox, R.M., Johnson, J.A. & Alexander, G.C. (2012).  Implications of high-frequency cochlear dead regions for fitting hearing aids to adults with mild to moderately severe hearing loss. Ear and Hearing 33(5), 573-87.

Hornsby, B. (2011) Dead regions and hearing aid fitting. Ask the Experts, Audiology Online October 3, 2011.

Huss, M. & Moore, B. (2005a). Dead regions and pitch perception. Journal of the Acoustical Society of America 117, 3841-3852.

Huss, M. & Moore, B. (2005b). Dead regions and noisiness of pure tones. International Journal of Audiology 44, 599-611.

Mackersie, C. L., Crocker, T. L. and Davis, R. A. (2004). Limiting high-frequency hearing aid gain in listeners with and without suspected cochlear dead regions. Journal of the American Academy of Audiology 15(7), 498-507.

Moore, B., Huss, M. & Vickers, D. (2000). A test for the diagnosis of dead regions in the cochlea. British Journal of Audiology 34, 205-224.

Moore, B. (2004). Dead regions in the cochlea: Conceptual foundations, diagnosis and clinical applications. Ear and Hearing 25, 98-116.

Moore, B. & Alcantara, J. (2001). The use of psychophysical tuning curves to explore dead regions in the cochlea. Ear and Hearing 22, 268-278.

Moore, B.C., Glasberg, B. & Vickers, D.A. (1999b). Further evaluation of a model of loudness perception applied to cochlear hearing loss. Journal of the Acoustical Society of America 106, 898-907.

Pepler, A., Munro, K., Lewis, K. & Kluk, K. (2014). Prevalence of Cochlear Dead Regions in New Referrals and Existing Adult Hearing Aid Users. Ear and Hearing 20(10), 1-11.

Schuknecht HF. Further observations on the pathology of presbycusis. Archives of Otolaryngology 1964;80:369—382

Vickers, D., Moore, B. & Baer, , T. (2001). Effects of low-pass filtering on the intelligibility of speech in quiet for people with and without dead regions at high frequencies. Journal of the Acoustical Society of America 110, 1164-1175.

Vinay and Moore, B. C. (2007). Speech recognition as a function of high-pass filter cutoff frequency for people with and without low-frequency cochlear dead regions. Journal of the Acoustical Society of America 122(1), 542-53.

Vinay, Baer, T. and Moore, B. C. (2008). Speech recognition in noise as a function of high pass-filter cutoff frequency for people with and without low-frequency cochlear dead regions. Journal of the Acoustical Society of America 123(2), 606-9.

Do the benefits of tinnitus therapy increase with time?

Parazzini, M., Del Bo, L., Jastreboff, M., Tognola, G. & Ravazzani, P. (2011). Open ear hearing aids in tinnitus therapy: An efficacy comparison with sound generators. International Journal of Audiology, 50(8), 548-553.

This editorial discusses the clinical implications of an independent research study and does not represent the opinions of the original authors.

Tinnitus management can include a variety of treatment approaches but the most effective usually include a combination of counseling and sound therapy (Jastreboff, 1990; Jastreboff & Hazell, 2004). For many individuals with hearing loss and tinnitus, hearing aids may be the only tinnitus treatment they participate in. Specific treatment recommendations vary depending on a number of patient characteristics, such as degree of hearing loss and severity of the tinnitus disturbance.

Tinnitus Retraining Therapy (TRT; Jastreboff, 1995; Henry et al., 2002, 2003; Jastreboff & Jastreboff, 2006) is a widely known therapeutic approach using counseling and sound therapy, based on the neurophysiological model of tinnitus, that stresses the importance of helping individuals understand their condition, reducing awareness and attention to the tinnitus, providing or restoring appropriate auditory input and eventually training the auditory system to habituate to the tinnitus. Jastreboff & Hazell (2004) have proposed a classification system in which patients are assigned to one of five categories: 0 = mild or recent tinnitus, 1 = normal hearing and severe tinnitus, 2 = significant hearing loss, 3 = hyperacusis and 4 = prolonged worsening of tinnitus or hyperacusis following sound exposure. A patient’s classification on this scale can guide treatment recommendations thereafter. Counseling educates patients about their hearing loss and tinnitus, helping them cope with the stress and annoyance of tinnitus in their everyday lives. Sound therapy treatment aims to help patients habituate to their tinnitus, employing ear-level sound generators for individuals without hearing loss (category 1; described above) whereas hearing aids are recommended for tinnitus sufferers with significant hearing loss (category 2).

Individuals who fall into the borderline area between categories 1 and 2 could theoretically be treated with either sound generators or hearing aids. Presently, there is little evidence to suggest that one of these approaches is superior to the other. Therefore, the purpose of Parazzini et al.’s study was to compare the efficacy of sound therapy treatments with sound generators versus open-fit hearing aids for tinnitus patients whose characteristics fall between categories 1 and 2.

91 participants completed the study. All participants met the requirements for tinnitus categorization between Jastreboff categories 1 and 2, with pure tone thresholds equal to or less than 25dB HL at 2kHz and greater than or equal to 25dB at frequencies higher than 2kHz. None of the participants had used hearing aids or been treated with tinnitus retraining therapy prior to the study. Participants were randomly assigned to one of two treatment groups: those fitted with small, ear-level sound generators (SG group) and those fitted with binaural open fit hearing aids (HA group). All participants used the devices for at least 8 hours per day. Participants completed the Tinnitus Handicap Inventory (THI; Newman et al., 1996) at each of four appointments scheduled at three-month intervals over a year. Structured interviews were completed at each visit. During these interviews the following variables were examined: the effect of tinnitus on life, tinnitus loudness and tinnitus annoyance.

Analysis revealed that participants showed a marked reduction in scores over time, beginning at the first session three months after initiation of therapy and continuing progressively over subsequent measurements every three months up to the last visit at 12 months.  Results with ear-level sound generators and those with hearing aids were essentially identical. All three variables decreased by approximately 50% from the initial assessment to the final session at 12 months. The mean THI score decreased 52% from 57.9 to 27.9, the effect of tinnitus on life decreased 51% from 6.5 to 3.2, and tinnitus loudness ratings decreased from 7 to 3.6, a reduction of 48%. The common clinical criteria for significant improvement on the THI is 20 points (Newman et al., 1998) and 62% of the participants in the current study reached this goal by 6 months and 74% reached it by 12 months. Applying a criterion of 40% improvement to reflect a reduction in tinnitus disturbance—as proposed by P.J. Jastreboff—51% of the subjects achieved the goal by 6 months and 72% reached it by 12 months.

For all recorded variables, the time of treatment was always statistically significant, indicating that subjects were improving steadily over time. There was never a significant difference based on the type of device, indicating that sound generators and open-fit hearing aids were equally successful at alleviating tinnitus symptoms and reactions, at least for the subjects in this population, whose characteristics fell between categories 1 and 2 in Jastreboff & Hazell’s classification system.

Parazzini and colleagues evaluated tinnitus sufferers with mild high frequency hearing loss and measured their responses for up to 12 months. Though there was no evidence of plateaus in the data, it remains unknown whether improvements would continue if treatment were to continue beyond this point. Longer term studies would be valuable to determine at what point improvements plateau and if longer measurement periods yield differences between hearing aids and sound generator devices.

The instruments used in Parazzini’s study were either sound generators or hearing aids; none of the devices had both features. Many hearing aids available today offer tinnitus masking stimuli along with traditional amplification features. A similar paradigm examining hearing aids as well as combination devices could offer practical insight into tinnitus treatment options with currently available hearing instrument product lines. Because a goal of tinnitus retraining therapy is to restore auditory inputs to reduce awareness of the tinnitus, hearing aids could have particular benefits over sound generators, because they stimulate the auditory system with meaningful environmental sounds which may more effective at drawing attention away from the tinnitus, in addition to masking the tinnitus with the amplified sound.

Open-fit, behind-the-ear hearing aids appear to be a good solution for tinnitus patients: the ear canal remains open and unoccluded, thereby reducing the likelihood of increased tinnitus awareness. Another consideration is whether receiver-in-canal (RIC) instruments would be an even better choice. RICs are equally as effective as traditional open-fit hearing aids at minimizing occlusion and offer the opportunity to provide a broader high frequency range and more stable high frequency gain than is available when sound is routed thin or standard thickness tubing (Alworth, et al., 2010). This opportunity to provide an extended high-frequency amplification would be expected to increase auditory input in the frequency range where tinnitus is often perceived. Therefore, RICs may more effectively mask the tinnitus via amplification of environmental sounds, reducing tinnitus awareness and potentially, tinnitus annoyance and stress.

Parazzini’s study offers strong support for the use of open-fit hearing aids with tinnitus patients. Advances in hearing aid technology, such as feedback management, automatic signal processing, and the availability of tinnitus masking stimuli may make modern hearing aids even better suited for this purpose. As mentioned earlier, many opportunities exist for research in the treatment of tinnitus with hearing aids: effects of hearing aid style, sound therapy parameters, treatment and counseling strategies, and duration of treatment all remain white space for future researchers.

References

Alworth, L.N., Plyler, P.N., Bertges-Reber, M. & Johnstone, P.M. (2010). Microphone, performance and subjective measures with open canal hearing instruments. Journal of the American Academy of Audiology 21(4), 249-266.

Del Bo, L. & Ambrosetti, U. (2007). Hearing aids for the treatment of tinnitus. Progress in Brain Research 166, 341-345.

Henry J.A., Jastreboff M.M., Jastreboff P.J., Schechter M.A. & Fausti S.A.(2002).  Assessment of patients for treatment with tinnitus retraining therapy. Journal of the American Academy of Audiology, 13, 523 – 44.

Henry J.A., Jastreboff M.M., Jastreboff P.J., Schechter M.A. & Fausti S.A. (2003). Guide to conducting tinnitus retraining therapy initial and follow-up interviews. Journal of Rehabilitation Research and Development 40, 157 – 177.

Jastreboff, P.J. (1990). Phantom auditory perception (tinnitus): Mechanisms of generation and perception. Neuroscience Research 8, 221-254.

Jastreboff, P.J. & Hazell, J.W.P. (2004). Tinnitus Retraining Therapy: Implementing the Neurophysiological Model. Cambridge University Press.

Jastreboff P.J. & Jastreboff M.M. 2006. Tinnitus retraining therapy: A different view on tinnitus. Otorhinolaryngology and Related Specialties 68, 23 – 29.

Newman, C.W., Jacobson, G.P. & Spitzer, J.B. (1996). Development of the Tinnitus Handicap Inventory. Archives of Otolaryngology Head Neck Surgery 122, 143-148.

Newman, C.W., Sandridge, S.A. & Jacobson, G.P. (1998). Psychometric adequacy of the Tinnitus Handicap Inventory (THI) for evaluating treatment outcome. Journal of the American Academy of Audiology 9, 153-160.

Parazzini, M., Del Bo, L., Jastreboff, M., Tognola, G. & Ravazzani, P. (2011). Open ear hearing aids in tinnitus therapy: An efficacy comparison with sound generators. International Journal of Audiology, 50(8), 548-553.

Hearing Aids Alone can be Adjusted to Help with Tinnitus Relief

Shekhawat, G.S., Searchfield, G.D., Kobayashi, K. & Stinear, C. (2013). Prescription of hearing aid output for tinnitus relief. International Journal of Audiology 2013, early online: 1-9.

This editorial discusses the clinical implications of an independent research study and does not represent the opinions of the original authors.

The American Tinnitus Association (ATA) reports that approximately 50 million people in the United States experience some degree of tinnitus.About one third of tinnitus sufferers consider it severe enough to seek medical attention. Fortunately only a small proportion of tinnitus sufferers experience symptoms that are debilitating enough that they feel they cannot function normally. But even if it does not cause debilitating symptoms, for many tinnitus still causes a number of disruptive effects such as sleep interference, difficulty concentrating, anxiety, frustration and depression  (Tyler & Baker, 1983; Stouffer & Tyler, 1990; Axelsson, 1992; Meikle 1992; Dobie, 2004).

Therapeutic treatments for tinnitus include the use of tinnitus maskers, tinnitus retraining therapy, biofeedback and counseling . Though these methods provide relief for many the tendency for tinnitus to co-occur with sensorineural hearing loss (Hoffman & Reed, 2004) leads the majority of individuals to attempt management of tinnitus with the use of hearing aids alone (Henry, et al., 2005; Kochkin & Tyler, 2008; Shekhawat et al., 2013).  There are a number of benefits that hearing aids may offer for individuals with tinnitus:  audiological counseling during the fitting process may provide the individual with a better understanding of hearing loss and tinnitus (Searchfield et al., 2010); hearing aids may reduce the stress related to struggling to hear and understand; amplification of environmental sound may reduce perceived loudness of tinnitus (Tyler, 2008).

Prescriptive hearing aid fitting procedures are designed to improve audibility and assist hearing loss rather than address tinnitus concerns. Yet the majority of studies show that hearing aids alone can be useful for tinnitus management (Shekhawat et al., 2013). The Better Hearing Institute reports that approximately 28% of hearing aid users achieve moderate to substantial tinnitus relief with hearing aid use (Tyler, 2008). Approximately 66% of these individuals said their hearing aids offered tinnitus relief most or all the time and 29% reported that their hearing aids relieved their tinnitus all the time. However, little is known about how hearing aids should be adjusted to optimize this apparent relief from tinnitus. In a study comparing DSL I/O v4.0 and NAL-NL1, Wise (2003) found that low compression kneepoints in the DSL formula reduced tinnitus awareness for 80% of subjects, but these settings also made environmental sounds more annoying. Conversely, they had higher word recognition scores with NAL-NL1 but did not receive equal tinnitus reduction. The proposed explanation for this was the increased low-intensity, low-frequency gain of the DSL I/O formula versus the increased high frequency emphasis of NAL-NL1. Based on these findings, the author suggested the use of separate programs for regular use and for tinnitus relief.

Shekhawat and his colleagues began to address the issue of prescriptive hearing aid fitting for tinnitus by studying how output characteristics should be tailored to meet the needs of hearing aid users with tinnitus.  Specifically, they examined how modifying the high frequency characteristics of the DSL v5 (Scollie et al., 2005) prescription would affect subjects’ short term tinnitus perception.  Speech files with variable high frequency cut-offs and gain settings were designed and presented to subjects in matched pairs to arrive at the most favorable configuration for tinnitus relief.

Twenty-five participants mild to moderate high-frequency sensorineural hearing loss were recruited for participation. None of the participants had used hearing aids before but all indicated interest in trying hearing aids to alleviate their tinnitus.  All subjects had experienced chronic, bothersome tinnitus for at least two years and the average perception of tinnitus loudness was 62.6 on a scale from 1-100, where 1 is very faint and 100 is very loud. Subjects had a mean Tinnitus Functional Index (TFI; Meikle et al., 2012) score of 39.30. Six participants reported unilateral tinnitus localized to the left side, 15 had bilateral tinnitus and 4 reported tinnitus that localized to the center of the head, which is likely to be present bilaterally though not necessarily symmetrical.  The majority (40%) of the subjects reported their tinnitus quality as tonal, whereas 28% described it as noise, 20% as crickets and 12% as a combination of sound qualities. Tinnitus pitch matching was conducted using pairs of tones in which subjects were repeatedly asked to indicate which of the tones more closely matched the pitch of their tinnitus. The average matched tinnitus pitch was 7.892kHz with a range from 800Hz to 14.5kHz. When asked to describe the pitch of their tinnitus, most subjects defined it as “very high pitched”, some said “high pitched” and some said “medium pitched”.

There were 13 speech files, based on sentences spoken by a female talker, with variable high frequency characteristics. There were three cut-off frequencies (2, 4 and 6kHz) and four high frequency gain settings (+6, +3, -3 and -6dB). Stimuli were presented via a master hearing aid with settings programmed to match DSL I/O v5.0 prescriptive targets for each subject’s hearing loss.  Pairs of sentences were presented in a round robin tournament procedure  and subjects were asked to choose which one interfered most with their tinnitus and made it less audible. A computer program tabulated the number of “wins” for each sentence and collapsed the information across subjects to determine a “winner”, or the sentence that was most effective at reducing tinnitus audibility.  Real-ear measures were used to compare DSL v5 prescribed settings with the characteristics of the winning sentence and outputs were recorded from 250Hz to 6000Hz.

The most preferred output for interfering with tinnitus perception was a 6dB reduction at 2kHz, which was chosen by 26.47% of the participants.  A 6dB reduction at 4kHz was preferred by 14.74% of the subjects, followed by a 3dB reduction at 2kHz, which was preferred by 11.76%.  There were no significant differences between the preferences for any of these settings.

They found that when tinnitus pitch was lower than 4kHz, the preferred setting had lower output than DSL v5 across the frequency range. The difference was small (1-3dB) and became smaller as tinnitus pitch increased. When tinnitus pitch was between 4-8kHz, subjects preferred slightly less output than DSL v5 for high frequencies and slightly more output for low frequencies, though these differences were minimal as well. When tinnitus pitch was higher than 8kHz, participants preferred output that was slightly greater than DSL v5 at three frequencies: 750Hz, 1kHz and 6kHz. From these results a trend emerged: as tinnitus pitch increased, preferred output became lower than DSL v5 though the differences were not statistically significant.

Few studies investigating the use of hearing aids for tinnitus management have considered the perceived pitch of the tinnitus or the prescriptive method of the hearing aids (Shekhawat et al., 2013). The results of this study suggest that DSL v5 could be an effective prescriptive formula for hearing aids used in a tinnitus treatment plan, though the pitch of the individual’s tinnitus might affect the optimal output settings. In general, they found that the higher the tinnitus pitch, the more the preferred output matched with DSL I.O v5.0 targets. This study agrees with an earlier report by Wise (2003) in which subjects preferred DSL v5 over NAL-NL1 for interfering with and reducing tinnitus. It is unknown how NAL-NL2 targets would fare in a similar comparison, though the NAL-NL2 formula may provide more tinnitus relief than its predecessor because it tends to prescribe slightly higher gain for low frequencies and lower compression ratios which could potentially provide more of a masking effect from environmental sounds. The NAL-NL2 formula should be studied as it pertains to tinnitus management, perhaps along with consideration of other factors including degree of loss, gender and prior experience with hearing aids, since these affect the targets prescribed by the updated formula (Keidser & Dillon, 2006; Keidser et al., 2008). The subjects in the present study had similar degrees of loss and all lacked prior experience with amplification; the NAL-NL2 formula takes these factors into consideration, prescribing slightly different gain based on degree of loss or for those who have used hearing aids before.

The authors recommend offering separate hearing aid programs for use when the listener desires tinnitus relief. Most fitting formulae are designed to optimize speech intelligibility and audibility, and based on previous reports, an individual might prefer one formula when speech understanding and communication is their top priority, and may prefer another, used with or without an added noise masker, when their tinnitus is bothering them.

They also propose that tinnitus pitch matching should be considered when programming hearing aids, though there is often quite a bit of variability in results and testing needs to be repeated several times to increase reliability.  Still, their study agrees with prior work in suggesting that the pitch of the tinnitus affects how likely hearing aids are to reduce it and whether output adjustments can impact how effective the hearing aids are to this end. Schaette (2010) found that individuals with tinnitus pitch lower than 6kHz showed more reduction of tinnitus with hearing aid use than did subjects whose pitch was higher than 6kHz. This makes sense because of the typical bandwidth of hearing aids, in which most gain is delivered below this frequency range. Not surprisingly, another study reported that hearing aids were most effective at reducing tinnitus when the pitch of the tinnitus was within the frequency response range of the hearing aids (McNeil et al., 2012).  Though incorporating tinnitus pitch matching into a clinical protocol might seem daunting or time consuming, it is probably possible to use an informal bracketing procedure, similar to one used for MCLs, to get an idea of the individual’s tinnitus pitch range. Testing can be repeated at subsequent visits to eventually arrive at a more reliable estimate.  If pitch matching measures are not possible, clinicians can question the patient about their perceived tinnitus pitch range and, with reference the current study, adjust outputs in the 2kHz to 4kHz range to determine if the individual experiences improvement in tinnitus relief.

Proposed are a series of considerations for fitting hearing instruments on tinnitus sufferers and for employing dedicated tinnitus programs:

- noise reduction should be disabled;

- fixed activation of omnidirectional microphones introduce more environmental noise;

- in contrast to the previous recommendation, full-time activation of directional microphones will increase the hearing aid noise floor;

- lower compression knee points increase amplification for softer sounds;

- expansion should be turned off to increase amplification of low-level background sound;

- efforts should be made to  minimize occlusion, which can emphasize the perception of tinnitus;

- ensuring physical comfort of the devices can minimize the user’s general awareness of their ears and the hearing aids, potentially reducing their attention to the tinnitus as well (Sheldrake & Jastreboff, 2004; Searchfield, 2006);

- user controls are important as they allow access to alternate hearing aid programs and sound therapy options.

Dr. Shekhawat and his colleagues also underscore the importance of counseling tinnitus sufferers who choose hearing aids. Clinicians need to ensure that these patients have realistic expectations about the potential benefits of hearing aids and that they know the devices will not cure their tinnitus. Follow-up care is especially important to determine if adjustments or further training is necessary to improve the performance of the aids for all of their intended purposes.

Currently, little is known about how to optimize hearing aid settings for tinnitus relief and there are no prescriptive recommendations targeted specifically for tinnitus sufferers. Shekhawat and his colleagues propose that the DSL v5 formula may be an appropriate starting point for these individuals, as their basic program and/or in an alternate program designated for use when their tinnitus is particularly bothersome.  Most importantly, however, are the observations that intentional manipulation of parameters common to most hearing aid fittings may increase likelihood of tinnitus relief with hearing aid use. Further investigation into the optimization of these fitting parameters may reveal a prescriptive combination that audiologists can leverage to benefit individuals with hearing loss who also seek relief from the stress and annoyance of tinnitus.

 

References

American Tinnitus Association (ATA) reporting data from the 1999-2004 National Health and Nutrition Examination Survey (NHANES), conducted by the Centers for Disease Control and Prevention (CDC). www.ata.org, retrieved 9-10-13.

Axelsson, A. (1992). Conclusion to Panel Discussion on Evaluation of Tinnitus Treatments. In J.M. Aran & R. Dauman (Eds) Tinnitus 91. Proceedings of the Fourth International Tinnitus Seminar (pp. 453-455). New York, NY: Kugler Publications.

Cornelisse, L.E., Seewald, R.C. & Jamieson, D.G. (1995). The input/output formula: A theoretical approach to the fitting of personal amplification devices. Journal of the Acoustical Society of America 97, 1854-1864.

Dobie, R.A. (2004). Overview: Suffering From Tinnitus. In J.B. Snow (Ed) Tinnitus: Theory and Management (pp.1-7). Lewiston, NY: BC Decker Inc.

Henry, J.A., Dennis, K.C. & Schechter, M.A. (2005). General review of tinnitus: Prevalence, mechanisms, effects and management. Journal of Speech, Language and Hearing Research 48, 1204-1235.

Hoffman, H.J. & Reed, G.W. (2004). Epidemiology of tinnitus. In: J.B. Snow (ed.) Tinnitus: Theory and Management. Hamilton, Ontario: BC Decker.

Keidser, G. & Dillon, H. (2006). What’s new in prescriptive fittings down under? In: Palmer, C.V., Seewald, R. (Eds.), Hearing Care for Adults 2006. Phonak AG, Stafa, Switzerland, pp. 133-142.

Keidser, G., O’Brien, A., Carter, L., McLelland, M. & Yeend, I. (2008). Variation in preferred gain with experience for hearing aid users. International Journal of Audiology 47(10), 621-635.

Kochkin, S. & Tyler, R. (2008). Tinnitus treatment and effectiveness of hearing aids: Hearing care professional perceptions. Hearing Review 15, 14-18.

McNeil, C., Tavora-Vieira, D., Alnafjan, F., Searchfield, G.D. & Welch, D. (2012). Tinnitus pitch, masking and the effectiveness of hearing aids for tinnitus therapy. International Journal of Audiology 51, 914-919.

Meikle, M.B. (1992). Methods for Evaluation of Tinnitus Relief Procedures. In J.M. Aran & R. Dauman (Eds.) Tinnitus 91: Proceedings of the Fourth International Tinnitus Seminar (pp. 555-562). New York, NY: Kugler Publications.

Meikle, M.B., Henry, J.A., Griest, S.E., Stewart, B.J., Abrams, H.B., McArdle, R., Myers, P.J., Newman, C.W., Sandridge, S., Turk, D.C., Folmer, R.L., Frederick, E.J., House, J.W., Jacobson, G.P., Kinney, S.E., Martin, W.H., Nagler, S.M., Reich, G.E., Searchfield, G., Sweetow, R. & Vernon, J.A. (2012). The Tinnitus Functional Index:  Development of a new clinical measure for chronic, intrusive tinnitus. Ear & Hearing 33(2), 153-176.

Moffat, G., Adjout, K., Gallego, S., Thai-Van, H. & Collet, L. (2009). Effects of hearing aid fitting on the perceptual characteristics of tinnitus. Hearing Research 254, 82-91.

Schaette, R., Konig, O., Hornig, D., Gross, M. & Kempter, R. (2010). Acoustic stimulation treatments against tinnitus could be most effective when tinnitus pitch is within the stimulated frequency range. Hearing Research 269, 95-101.

Shekhawat, G.S., Searchfield, G.D., Kobayashi, K. & Stinear, C. (2013). Prescription of hearing aid output for tinnitus relief. International Journal of Audiology 2013, early online: 1-9.

Shekhawat, G.S., Searchfield, G.D. & Stinear, C.M. In press (2013). Role of hearing aids in tinnitus intervention: A scoping review. Journal of the American Academy of Audiology.

Searchfield, G.D. (2006). Hearing aids and tinnitus. In: R.S. Tyler (ed). Tinnitus Treatment, Clinical Protocols. New York: Thieme Medical Publishers, pp. 161-175.

Searchfield, G.D., Kaur, M. & Martin, W.H. (2010). Hearing aids as an adjunct to counseling: Tinnitus patients who choose amplification do better than those that don’t. International Journal of Audiology 49, 574-579.

Sheldrake, J.B. & Jastreboff, M.M. (2004). Role of hearing aids in management of tinnitus. In: J.B. Sheldrake, Jr. (ed.) Tinnitus: Theory and Management. London: BC Decker Inc, pp. 310-313.

Stouffer, J.L. & Tyler, R. (1990). Characterization of tinnitus by tinnitus patients. Journal of Speech and Hearing Disorders 55, 439-453.

Tyler, R.S.(Ed). (2008). The Consumer Handbook on Tinnitus. Auricle Ink Publishers., Sedona, AZ.

Tyler, R. & Baker, L.J. (1983). Difficulties experienced by tinnitus sufferers. Journal of Speech and Hearing Disorders 48, 150-154.

Wise, K. (2003). Amplification of sound for tinnitus management: A comparison of DSL i/o and NAL-NL1 prescriptive procedures and the influence of compression threshold on tinnitus audibility. Section of Audiology, Auckland: University of Auckland.

 

Does lip reading take the effort out of speech understanding?

Picou, E.M., Ricketts, T.A. & Hornsby, B.W.Y. (2013). How hearing aids, background noise and visual cues influence objective listening effort. Ear and Hearing, in press.

This editorial discusses the clinical implications of an independent research study and does not represent the opinions of the original authors.

For many people with hearing loss, visual cues from lip-reading are a valuable cue that has been proven to improve speech recognition across a variety of listening conditions (Sumby & Pollock, 1954; Erber, 1975; Grant, et al., 1998). To date is has remained unclear how visual cues, background noise, and hearing aid use interact with each other to affect listening effort.

Listening effort is often described as the allocation of additional cognitive resources to the task of understanding speech. If cognitive resources are finite or limited, then two or more simultaneous tasks will be in competition with each other for cognitive resources. Decrements in performance on one task can be interpreted as an allocation of resources away from the task and toward another concurrent task. Therefore, listening effort is often measured with dual-task paradigms, in which listeners respond to speech stimuli while simultaneously performing another task or responding to another kind of stimulus. Allocation of cognitive resources in this way is thought to represent a competition for working memory resources (Baddeley & Hitch, 1974; Baddeley, 2000).

The Ease of Language Understanding (ELU) model states that the process of understanding language involves matching phonological, syntactic, semantic and prosodic information to stored templates in long-term memory. When there is a mismatch between the incoming sensory information and the stored template, additional effort must be exerted to resolve the ambiguity of the message. This additional listening effort taxes working memory resources and may require the listener to allocate fewer resources to other tasks. Several studies have identified conditions that degrade a speech signal, such as background noise (Murphy, et al., 2000; Larsby et al., 2005; Zekveld et al., 2010) and hearing loss (Rabbitt, 1990; McCoy et al., 2005) in a manner that increases listening effort.

Individuals with reduced working memory capacity may be more negatively affected by conditions that degrade a speech signal. Previous reports have suggested that differences in working memory capacity hold a relationship to speech recognition in noise and performance with hearing aids in noise (Lunner, 2003; Foo et al., 2007).  The speed of retrieval from long-term memory may also affect performance and listening effort in adverse listening conditions (Van Rooij et al., 1989; Lunner, 2003). Because sensory inputs decay rapidly (Cowan, 1984), listeners with slow processing speed might not be able to fully process incoming information and match it to long term memory stores before it decays. Therefore, they would have to allocate more effort and resources to the task of matching sensory input to long-term memory templates.

Just as some listener traits might be expected to increase listening effort, some factors might offset adverse listening conditions by providing more information to support the matching of incoming sensory inputs to long-term memory. The use of visual cues is well known to improve speech recognition performance and some studies indicate that individuals with large working memory capacities are better able to make use of visual cues from lipreading (Picou et al., 2011).  Additionally, listeners who are better lipreaders may require fewer cognitive resources to understand speech, allowing them to make better use of visual cues in noisy environments (Hasher & Zacks, 1979; Picou et al., 2011).

The purpose of Picou, Ricketts and Hornsby’s study was to examine how listening effort is affected by hearing aid use, visual cues and background noise. A secondary goal of the study was to determine how specific listener traits such as verbal processing speed, working memory and lipreading ability would affect the measured changes in listening effort.

Twenty-seven hearing-impaired adults participated in the study. All were experienced hearing aid users and had corrected binocular vision of 20/40 or better. Participants were fitted with bilateral behind-the-ear hearing aids with non-occluding, non-custom eartips. Advanced features such as directionality and noise reduction were turned off, though feedback management was left on in order to maximize usable gain. Hearing aids were programmed with linear settings to eliminate any potential effect of amplitude compression on listening effort, a relationship which is as of yet unestablished.

A dual-task paradigm with a primary speech recognition task and secondary visual reaction time task was used to measure listening effort. The speech recognition task used monosyllabic words spoken by a female talker (Picou, 2011), presented at 65dB in the presence of multi-talker babble. Prior to the speech recognition task, individual SNRs for auditory only (AO) and auditory-visual (AV) conditions were determined at levels that yielded performance between 50-70% correct, because scores in this range are most likely to show changes in listening effort (Gatehouse & Gordon, 1990).

The reaction time task required participants to press a button in response to a rectangular visual probe that occurred prior to presentation of the speech token. The visual probe was presented prior to the speech tokens, so that the probe would not distract from the use of visual cues during the speech recognition task. The visual and speech stimuli were presented within a narrow enough interval (less than 500 msec) so that cognitive resources would have to be expended for both tasks at the same time (Hick & Tharpe, 2002).

Three listener traits were examined with regard to listening effort in quiet and noisy conditions, with and without visual cues. Visual working memory was evaluated with the Automated Operation Span (AOSPAN) test (Unsworth et al., 2005). The AOSPAN requires subjects to solve math equations and memorize letters. After seeing a math equation and identifying the answer, subjects are shown a letter which disappears after 800 msec. Following a series of equations they are then asked to identify the letters that they saw, in the order that they appeared. Scores are based on the number of letters that are recalled correctly.

Verbal processing speed was assessed with a lexical decision task (LDT) in which subjects were presented with a string of letters and were asked to indicate, as quickly as possible, if the letters formed a real word.  The test consisted of 50 common monosyllabic English words and 50 monosyllabic nonwords. The task reflects verbal processing speed because it requires the participant to match the stimuli to representations of familiar words stored in long-term memory (Meyer & Schvaneveldt, 1971; Milberg & Blumstein, 1981; Van Rooij et al., 1989). The reaction time to respond to the stimuli was used as a measure of verbal processing speed.

Finally, lipreading ability was measured with the Revised Shortened Utley Sentence Lipreading Test (ReSULT; Updike, 1989). The test required participants to repeat sentences spoken by a female talker, when the talker’s face was visible but speech was inaudible. Responses were scored based on the number of words repeated correctly in each sentence.

Subjects participated in two test sessions. At the first session, vision and hearing was tested, individual SNR levels were determined for the speech recognition task and AOSPAN, LDT and ReSULT scores were obtained.  At the second session, subjects completed practice sequences with AO and AV stimuli, then the dual speech recognition and visual reaction time tests were administered in eight counterbalanced conditions listed below. Due to the number of experimental conditions, only select outcomes of this study will be reviewed.

1.         auditory only in quiet, unaided

2.         auditory only in noise, unaided

3.         auditory-visual in quiet, unaided

4.         auditory-visual in noise, unaided

5.         auditory only in quiet, aided

6.         auditory only in noise, aided

7.         auditory-visual in quiet, aided

8.         auditory-visual in noise, aided

The main analysis showed that background noise impaired performance in all conditions and hearing aid use and visual cues improved performance. However, there were significant interactions between hearing aid use and visual cues, hearing aids and background noise, and visual cues and background noise, indicating that the effect of hearing aid use depended on the test modality (AV or AO), and background noise (present or absent), and the effect of visual cues depended on background noise (present or absent).  Hearing aid benefit proved to be larger in AO conditions than in AV conditions and was larger in quiet conditions than in noisy conditions.  The effect of noise was greater in the AV conditions than in the AO conditions, but the authors suggest that this could have been related to the individualized SNRs chosen for the test procedure.

On the reaction time task, background noise increased listening effort and hearing aid use reduced listening effort, though there was high variability and the effects of both variables were small. Additional analysis determined that the individual SNRs chosen for the dual task did not affect the hearing aid benefits that were measured. The availability of visual cues did not change overall reaction times and it was therefore determined that visual cues did not affect listening effort in this task of reaction time.

With regard to listening effort benefits derived from hearing aid use, the performance in quiet conditions was strongly related to performance in noise. In other words, subjects who obtained benefit from hearing aid use in quiet also obtained benefit in noise and individuals with slower verbal processing speed were more likely to derive benefit from hearing aid use. With regard to visual cues, there were several correlations with listener traits. Subjects who were better lipreaders derived more benefit from visual cues and those with smaller working memory capacities also showed more benefit from visual cues. These correlations were significant in quiet and noisy conditions. For quiet conditions, there was a positive correlation between verbal processing speed and benefit from visual cues, with better verbal processors showing more benefit from visual cues. There were no correlations between background noise and any of the measured listener traits.

The overall findings that visual cues and hearing aid use had positive effects and background noise had a negative effect on speech perception performance were not surprising. Similarly, the findings that hearing aid benefit was reduced for AV conditions versus AO conditions and for noisy versus quiet conditions were consistent with previous reports (Cox & Alexander, 1991; Walden et al., 2001; Duquesnoy & Plomp, 1983).  Because hearing aid use improves audibility, visual cues might not have been needed as much as they were in unaided conditions and the presence of noise may have counteracted the improved audibility by masking a portion of the speech cues needed for correct understanding, especially with the omnidirectional, linear instruments used in this study.

The ability of hearing aids to decrease listening effort was significant, in keeping with previously published results, but the improvements were lesser than than those reported in some previous studies. This could be related to the non-simultaneous timing of the tasks in the dual-task paradigm, but the authors surmise that it could be related to the way their subjects’ hearing aids were programmed. In most previous studies, individuals used their own hearing aids, set to individually prescribed and modified settings. In the current study, all participants used the same hearing aid circuit set to linear, unmodified targets. Advanced features like directionality and noise reduction, which are likely to impact listening effort (Sarampalis, 2009), speech discrimination ability and perceived ease of listening in everyday situations, were turned off.

There was a significant relationship between verbal processing speed and hearing aid benefit, in that subjects with slower processing speed were more likely to benefit from hearing aid use.  Sensory input decays rapidly and requires additional cognitive effort when it is mismatched with long-term memory stores. Any factor that improves the sensory input may facilitate the matching process. The authors posited that slow verbal processors might benefit more from amplification because hearing aids improved the quality of the sensory input, thereby reducing the cognitive effort and time that would otherwise be required to match the input to long-term memory templates.

On average, the availability of visual cues did not have a significant effect on listening effort. This may be a surprising result given the well-known positive effects of visual cues for speech recognition. However, there was high variability among subjects and it was apparent that better lipreaders were more able to make use of visual cues, especially in quiet conditions without hearing aids. Working memory capacity was negatively correlated with benefit from visual cues, indicating that subjects with better working memory capacity derived less benefit from visual cues on average. The relationship between these variables is unclear, but the authors suggest that individuals with lower working memory capacities may be more susceptible to changes in listening effort and therefore more likely to benefit from additional sensory information such as visual cues.

Understanding how individual traits affect listening effort and susceptibility to noise is important to audiologists for a number of reasons, partly because we often work with older individuals. Working memory declines as a result of the normal aging process and may begin in middle age (Wang, et al., 2011).  Similarly, the speed of cognitive processing slows and visual impairment becomes more likely with increasing age (Clay, et al., 2009). Many patients seeking audiological care may also suffer from these deficits in working memory, verbal processing, and visual acuity. Though more research is needed to understand how these variables relate to one another, they should be considered in clinical evaluations and hearing aid fittings.  Advanced hearing aid features that counteract the degrading effects of noise and reverberation may be particularly important for elderly or visually impaired hearing aid users. As shown in the reviewed study, these patients will benefit significantly from face-to-face conversation, slow speaking rates and reduced environmental distractions. Counseling sessions should include discussion of these issues so that patients and family members understand how they can use strategic listening techniques, in addition to hearing aids, to improve speech recognition and reduce cognitive effort.

References

Clay, O., Edwards, J., Ross, L., Okonkwo, O., Wadley, V., Roth, D. & Ball, K. (2009). Visual function and cognitive speed of processing mediate age-related decline in memory span and fluid intelligence. Journal of Aging and Health 21(4), 547-566.

Cox, R.M. & Alexander, G.C. (1991).  Hearing aid benefit in everyday environments. Ear and Hearing 12, 127-139.

Downs, D.W. (1982). Effects of hearing aid use on speech discrimination and listening effort. Journal of Speech and Hearing Disorders 47, 189-193.

Duquesnoy, A.J. & Plomp, R. (1983). The effect of a hearing aid on the speech reception threshold of hearing impaired listeners in quiet and in noise. Journal of the Acoustical Society of America 73, 2166-2173.

Erber, N.P. (1975). Auditory-visual perception of speech. Journal of Speech and Hearing Disorders 40, 481-492.

Foo, C., Rudner, M. & Ronnberg, J. (2007). Recognition of speech in noise with new hearing instrument compression release settings requires explicit cognitive storage and processing capacity. Journal of the American Academy of Audiology 18, 618-631.

Gatehouse, S., Naylor, G. & Elberling, C. (2003). Benefits from hearing aids in relation to the interaction between the user and the environment. International Journal of Audiology 42 Suppl 1, S77-S85.

Gatehouse, S. & Gordon, J. (1990). Response times to speech stimuli as measures of benefit from amplification. British Journal of Audiology 24, 63-68.

Grant, K.W., Walden, B.F. & Seitz, P.F. (1998).  Auditory visual speech recognition by hearing impaired subjects. Consonant recognition, sentence recognition and auditory-visual integration. Journal of the Acoustical Society of America 103, 2677-2690.

Hick, C.B. & Tharpe, A.M. (2002). Listening effort and fatigue in school-age children with and without hearing loss. Journal of Speech, Language and Hearing Research 45, 573-584.

Hornsby, B.W.Y. (2013).  The Effects of Hearing Aid Use on Listening Effort and Mental Fatigue Associated with Sustained Speech Processing Demands. Ear and Hearing, in press.

Meyer, D.E. & Schvaneveldt, R.W. (1971). Facilitation in recognizing pairs of words: Evidence of a dependence between retrieval operations. Journal of Experimental Psychology 90, 227-234.

Milberg, W. & Blumstein, S.E. (1981). Lexical decision and aphasia: Evidence for semantic processing. Brain and Language 14, 371-385.

Picou, F.M., Ricketts, T.A. & Hornsby, B.W.Y (2011). Visual cues and listening effort: Individual variability. Journal of Speech, Language and Hearing Research 54, 1416-1430.

Picou, E.M., Ricketts, T.A. & Hornsby, B.W.Y. (2013). How hearing aids, background noise and visual cues influence objective listening effort. Ear and Hearing, in press.

Rudner, M., Foo, C. & Ronnberg, J. (2009). Cognition and aided speech recognition in noise: Specific role for cognitive factors following nine week experience with adjusted compression settings in hearing aids. Scandinavian Journal of Psychology 50, 405-418.

Sarampalis, A., Kalluri, S., Edwards, B. & Hafter, E. (2009) Objective measures of listening effort: effects of background noise and noise reduction. Journal of Speech, Language, and Hearing Research 52, 1230–1240.

Sumby, W.H. & Pollock, I. (1954). Visual contribution to speech intelligibility in noise. Journal of the Acoustical Society of America 26, 212-215.

Unsworth, N., Heitz, R.P. & Schrock, J.C. (2005). An automated version of the operation span task. Behavioral Research Methods 37, 498-505.

Van Rooij, J.C., Plomp, R. & Orlebeke, J.F. (1989).  Auditive and cognitive factors in speech perception by elderly listeners. I: Development of test battery. Journal of the Acoustical Society of America 86, 1294-1309.

Walden, B.F., Grant, K.W. & Cord, M.T. (2001). Effects of amplification and speechreading on consonant recognition by persons with impaired hearing. Ear and Hearing 22, 333-341.

Wang, M., Gamo, N., Yang, Y., Jin, L., Wang, X., Laubach, M., Mazer, J., Lee, D. & Arnsten, A. (2011). Neuronal basis of age-related working memory decline. Nature 476, 210-213.

The Tinnitus Functional Index (TFI): A New and Improved way to Evaluate Tinnitus

Meikle, M.B., Henry, J.A., Griest, S.E., Stewart, B.J., Abrams, H.B., McArdle, R., Myers, P.J., Newman, C.W., Sandridge, S., Turk, D.C., Folmer, R.L., Frederick, E.J., House, J.W., Jacobson, G.P., Kinney, S.E., Martin, W.H., Nagler, S.M., Reich, G.E., Searchfield, G., Sweetow, R. & Vernon, J.A. (2012). The Tinnitus Functional Index:  Development of a new clinical measure for chronic, intrusive tinnitus. Ear & Hearing 33(2), 153-176.

This editorial discusses the clinical implications of an independent research study and does not represent the opinions of the original authors.

The practice of clinical audiology can arguably be described as having two primary goals: the diagnosis of auditory and vestibular disorders, followed by verifiable, effective treatment and rehabilitation. There are well established, objective diagnostic tests for hearing and vestibular disorders and their treatment methods can be verified with objective and subjective tools. The evaluation and treatment of tinnitus, though equally important, is more complicated. There are test protocols for matching perceived tinnitus characteristics, but the impact of tinnitus on the individual must be measured subjectively with self-assessment questionnaires.  There are several published questionnaires to evaluate tinnitus severity and the impact it has on an individual’s activities, emotions and relationships. However, most of these questionnaires were not designed specifically to measure the effect of tinnitus treatments (Kamalski et al., 2010), so their value as follow-up measures is unknown.

Tinnitus affects as many as 50 million Americans and can have disabling effects including: sleep interference, difficulty concentrating and attending, anxiety, frustration and depression (for review see Tyler & Baker, 1983; Stouffer & Tyler, 1990; Axelsson, 1992; Meikle 1992; Dobie, 2004b). There are numerous methods of treatment available, including hearing aids, tinnitus maskers, tinnitus retraining therapy, biofeedback, counseling and others. Because there is currently no standard assessment tool to evaluate tinnitus treatment outcomes, the effectiveness of tinnitus treatment methods is difficult to verify and compare. The Tinnitus Functional Index (TFI) was developed as a collaborative effort among researchers and clinicians to develop a validated, standard questionnaire that can be used clinically for intake assessments and follow-up measurements and in the laboratory as a way of comparing treatment efficacy and identifying subject characteristics.

The developers of the TFI aimed for this inventory to be used in three ways:

1. As an intake evaluation tool to identify individual differences in tinnitus patients.
2. As a reliable and valid measurement of multiple domains of tinnitus severity.
3. As an outcome measure to assess treatment-related change in tinnitus.

The study, supported by a grant from the Tinnitus Research Consortium (TRC), had three stages. The first stage involved consultation with 21 tinnitus experts, including audiologists, otologists and hearing researchers. The panel of experts evaluated 175 items from nine previously published tinnitus questionnaires and judged them based on their relevance to 10 tinnitus negative impact domains as well as their expected responsiveness, or ability to measure treatment-related improvement. After analyzing the content validity, relevance and potential responsiveness of the 175 items (Haynes et al., 1995), 43 items were selected for the first questionnaire prototype. The TRC initially required that 10 domains of negative tinnitus impact be covered by the TFI but this expert panel added three additional domains so that the first prototype of the TFI covered 13 domains of tinnitus impact. The TRC also recommended avoiding overly negative items (such as those referring to suicidal thoughts or feeling victimized or helpless), items referring to hearing loss without mentioning tinnitus and items referring to more than one subtopic. Each domain had at least three or four items, based on recommendations for achieving adequate reliability (Fabrigar et al., 1999; Moran et al., 2001).  Each questionnaire item probed respondents for a rating on a scale of 0 to 10, based on how they experienced their tinnitus “over the past week”. For example, a typical question read, “Over the past week, how easy was it for you to cope with your tinnitus?” with potential responses from 0 being “very easy to cope” and 10 being “impossible to cope”.

During the second stage of the study, TFI Prototype 1 was tested on 326 tinnitus patients at five independent clinical sites.  The goals for the second stage were to determine the responsiveness of items or their ability to reflect changes in tinnitus status, to evaluate the 13 tinnitus impact domains and to determine the TFI’s ability to scale tinnitus severity. The questionnaire was administered at the initial intake assessment, after 3 months and after 6 months.  In addition to completing the TFI, at the initial encounter the subjects completed a brief tinnitus history questionnaire, The Tinnitus Handicap Inventory (THI; Newman et al., 1996) and the Beck Depression Inventory-Primary Care (BDEI-PC; Beck et al., 1997).  The TFI was re-administered to 65 subjects after 3 months and again to 42 subjects after 6 months.

The researchers found that subjects had very few problems responding to the 43 selected items and that most questionnaires were fully completed. There were no floor or ceiling effects, indicating that there were no items for which responses clustered at either end of the scale, reducing the potential responsiveness of the item.  The TFI had very high convergent validity, which means it agreed well with other published scales of tinnitus severity, such as the THI.  There were large effect sizes, demonstrating that the Prototype 1 items had good responsiveness for treatment-related change and supporting use of the TFI as an outcome measure. Factor analysis of the 13 initial tinnitus impact domains yielded 8 clearly structured domains, which were retained for the second prototype.

The third stage of the study involved development and evaluation of TFI Prototype 2, which was modified based on validity and reliability measurements from the first prototype. Prototype 2 included the 30 best-functioning items from the first version, categorized according to 8 tinnitus impact domains. It was administered to 347 new participants at the initial assessment. Follow-up data were obtained from 155 participants after 3 months and from 85 participants after 6-months. Encouragingly, the results from clinical evaluation of Prototype 2 again showed good performance for all of the validity and reliability measurements, supporting its use for scaling tinnitus severity.

The best performing items from Prototype 2 were used to create the final version of the TFI, which contains 25 items in 8 domains or sub-scales: Intrusive, Sense of Control, Cognitive, Sleep, Auditory, Relaxation, Quality of Life and Emotional. Seven of the domains contain 3 items and the Quality of Life domain contains 4 items.

When used during the initial assessment, the TFI categorizes tinnitus severity according to five levels: not a problem, a small problem, a moderate problem, a big problem or a very big problem.  As a screening tool, this allows a clinician to determine the overall severity of the tinnitus to help formulate a treatment plan and consider whether referrals to other clinical professionals are needed. For example, an individual who scores in the “not a problem” level may require only brief reassurance and counseling and may be asked to follow-up only if symptoms progress. In contrast, an individual who scores in the “big problem” or “very big problem” categories will likely need referrals for additional diagnostic and therapeutic services right away.

The developers of the TFI acknowledge that their study is preliminary and more research is needed to determine the TFI’s value as an outcome measurement tool. However, based on their analyses they recommend that a change in TFI score of 13 should be considered meaningful. In other words, a decrease of 13 or more indicates an improvement based on treatment recommendations or an increase in 13 or more indicates a significant exacerbation of symptoms.

Most tinnitus self-report questionnaires were designed to assess tinnitus impact but do not specifically measure treatment outcomes. The Tinnitus Handicap Inventory (THI; Newman et al., 1996), however, has shown some promise as an initial evaluation tool and as a way to measure treatment outcome.  After formulation of the final version of the TFI, the effect sizes of the TFI were compared to the THI. Overall, the TFI had greater responsiveness, indicating that it could potentially yield statistically significant differences with fewer subjects than the THI would require. Evaluation of subs-scale domains yielded some differences between the TFI and THI, primarily related to the “Catastrophic” subscale of the THI. Most of these items were not included in the TFI, based on the TRC’s recommendations to avoid questions dealing with negative ideation. The TRC recommended against inclusion of items relating to despair inability to escape tinnitus and fear of having a terrible disease, because they may suggest to people with mild tinnitus that they will eventually have these concerns, creating feelings of negativity before treatment has started.  Because these items on the THI correlated only moderately with the more neutrally worded items on the TFI, the authors suggested that the THI Catastrophic subscale might measure a different severity domain than the TFI and may be useful in combination with the THI as an outcome measure.

The Tinnitus Functional Index (TFI), like other previously published tinnitus questionnaires, shows promise as a tool to measure and classify tinnitus severity. It is easy for respondents to understand the test items and can be administered briefly at or prior to the initial appointment. An additional benefit of the TFI appears to be its validity as an outcome measure of treatment effectiveness. This is critically important for guiding clinical decisions and modifying ongoing treatment plans. It also suggests that the TFI could be useful in laboratory research as a standardized way to evaluate and compare tinnitus treatment methods or to identify subject characteristics for inclusion in treatment groups. For instance, if a treatment is expected to affect the negative emotional impact of tinnitus more than the functional impact, the TFI could be useful in identifying appropriate subject candidates who are experiencing strong emotional reactions to their tinnitus. The Tinnitus Functional Index (TFI) is one of the most systematically validated methods of assessing a patient’s reaction to their tinnitus. Ease of application and interpretation place the TFI among the most compelling assessment options for clinicians working with tinnitus patients.

If you would like to use the TFI. It is now available on a website posted by Oregon Health & Science University (OHSU). OHSU owns the copyright to the TFI and permission is required by OHSU to use the TFI. The request form takes 3 minutes to complete and allows you access to the TFI form and instructions. You will then be able to use the TFI with no fee.

http://www.ohsu.edu/xd/health/services/ent/services/tinnitus-clinic/tinnitus-functional-index.cfm

References

Axelsson, A. (1992). Conclusion to Panel Discussion on Evaluation of Tinnitus Treatments. In J.M. Aran & R. Dauman (Eds) Tinnitus 91. Proceedings of the Fourth International Tinnitus Seminar (pp. 453-455). New York, NY: Kugler Publications.

Beck, A.T., Guth, D. & Steer, R.A. (1997). Screening for major depression disorders in medical in patients with the Beck Depression Inventory for Primary Care. Behavioral Research and Therapy 35, 785-791.

Dobie, R.A. (2004b). Overview: Suffering From Tinnitus. In J.B. Snow (Ed) Tinnitus: Theory and Management (pp.1-7). Lewiston, NY: BC Decker Inc.

Fabrigar, L.R., Wegeners, D.T. & MacCallum, R.C. (1999). Evaluating the use of exploratory factor analysis in psychological research. Psychological Methods 4, 272-299.

Kamalski, D.M., Hoekstra, C.E. & VanZanten, B.G. (2010). Measuring disease-specific health-related quality of life to evaluate treatment outcomes in tinnitus patients: A systematic review. Otolaryngology Head and Neck Surgery 143, 181-185.

Meikle, M.B. (1992). Methods for Evaluation of Tinnitus Relief Procedures. In J.M. Aran & R. Dauman (Eds.) Tinnitus 91: Proceedings of the Fourth International Tinnitus Seminar (pp. 555-562). New York, NY: Kugler Publications.

Meikle, M.B., Henry, J.A., Griest, S.E., Stewart, B.J., Abrams, H.B., McArdle, R., Myers, P.J., Newman, C.W., Sandridge, S., Turk, D.C., Folmer, R.L., Frederick, E.J., House, J.W., Jacobson, G.P., Kinney, S.E., Martin, W.H., Nagler, S.M., Reich, G.E., Searchfield, G., Sweetow, R. & Vernon, J.A. (2012). The Tinnitus Functional Index:  Development of a new clinical measure for chronic, intrusive tinnitus. Ear & Hearing 33(2), 153-176.

Moran, L.A., Guyatt, G.H. & Norman, G.R. (2001). Establishing the minimal number of items for a responsive, valid, health-related quality of life instrument. Journal of Clinical Epidemiology 54, 571-579.

Newman, C.W., Jacobson, G.P. & Spitzer, J.B. (1996). Development of the Tinnitus Handicap Inventory. Archives of Otolaryngology Head and Neck Surgery 122, 143-148.

Stouffer, J.L. & Tyler, R. (1990). Characterization of tinnitus by tinnitus patients. Journal of Speech and Hearing Disorders 55, 439-453.

Tyler, R. & Baker, L.J. (1983). Difficulties experienced by tinnitus sufferers. Journal of Speech and Hearing Disorders 48, 150-154.

The Top 5 Audiology Research Articles from 2012

2012 was an impressive year for scientific publication in audiology research and hearing aids. Narrowing the selection to 15 or 20 articles was far easier than selecting 5 top contenders. After some thought and discussion, here is our selection of the top 5 articles published in 2012.


1. Implications of high-frequency cochlear dead regions for fitting hearing aids to adults with mild to moderately severe hearing loss

Cox, R.M., Johnson, J.A., & Alexander, G.C. (2012). Implications of high-frequency cochlear dead regions for fitting hearing aids to adults with mild to moderately severe hearing loss. Ear and Hearing, 33, 573-587.

This article is the second in a series that investigated relationships between cochlear dead regions and benefits received from hearing aids. A sample of patients, diagnosed with high-frequency cochlear dead regions, demonstrated superior outcomes when prescribed hearing aids with a broadband response; as compared to a response that limited audibility at 1,000 Hz. These findings clearly illustrate that patients with cochlear dead regions benefit from—and prefer—amplification at frequencies similar to those with diagnosed cochlear dead regions.

http://journals.lww.com/ear-hearing/Abstract/2012/09000/Implications_of_High_Frequency_Cochlear_Dead.2.aspx

2. The speech intelligibility index and the pure-tone average as predictors of lexical ability in children fit with hearing aids

Stiles, D.J., Bentler, R.A., & McGregor, K.K. (2012). The speech intelligibility index and the pure-tone average as predictors of lexical ability in children fit with hearing aids. Journal of Speech Language and Hearing Research, 55, 764-778.

The pure-tone threshold is the most commonly referenced diagnostic information when counseling families of children with hearing loss. This study compared the predictive value of pure-tone thresholds and the aided speech intelligibility index for a group of children with hearing loss. The aided speech intelligibility index proved to be a stronger predictor of word recognition, word repetition, and vocabulary. These observations suggest that a measure of aided speech intelligibility index is useful tool in hearing aid fitting and family counseling.

http://jslhr.asha.org/cgi/content/abstract/55/3/764

3. NAL-NL2 Empirical Adjustments

Keidser, G., Dillon, H., Carter, L., & O’Brien, A. (2012). NAL-NL2 Empirical Adjustments. Trends in Amplification, 16(4), 211-223.

The NAL-NL2 relies on several psychoacoustic models to derive target gains for a given hearing loss. Yet, it is well understood that these models are limiting and do not account for many individual factors. The inclusion of empirical adjustments to the NAL-NL2 highlights several factors that should be considered for prescribing gain to hearing aid users.

http://tia.sagepub.com/content/16/4/211.abstract

4. Initial-fit approach versus verified prescription: Comparing self-perceived hearing aid benefit

Abrams, H.B., Chisolm, T.H., McManus, M., & McArdle, R. (2012). Initial-fit approach versus verified prescription: Comparing self-perceived hearing aid benefit. Journal of the American Academy of Audiology, 23(10), 768-778.

While the outcomes of this study were not surprising, similar data had not been published in the refereed literature. The authors show that patients fit to a prescriptive target (i.e. NAL-NL1) report significantly better outcomes than patients fit to the lower gain targets that are offered in fitting softwares as ‘first-fit’ prescriptions. This study is a testimonial to the importance of counseling patients regarding audibility and the necessity of real-ear measurement to ensure audibility.

http://aaa.publisher.ingentaconnect.com/content/aaa/jaaa/2012/00000023/00000010/art00003

5. Conducting qualitative research in audiology: A tutorial

Knudsen, L.V., Laplante-Levesque, A., Jones, L., Preminger, J.E., Nielsen, C., Lunner, T., Hickson, L., Naylor, G., & Kramer, S.E. (2012). Conducting qualitative research in audiology: A tutorial. International Journal of Audiology, 51, 83-92.

A substantive majority of the audiologic research literature reports on quantitative data, discussing group outcomes and average trends. The challenges faced in capturing individual differences and clearly documenting field experiences require a different approach to data collection and analysis. Qualitative analysis leverages data from transcribed interviews or subjective reports to probe these anecdotal reports. This tutorial paper described methods for qualitative analysis and cites existing studies that have used these analyses.

http://informahealthcare.com.ezproxylocal.library.nova.edu/doi/abs/10.3109/14992027.2011.606283

The Speech, Spatial and Qualities of Hearing Scale (SSQ): A Gatehouse Legacy

Gatehouse, S. & Noble, W. (2004). The speech, spatial and qualities of hearing scale (SSQ). International Journal of Audiology, 43, 85-99.

This editorial discusses the clinical implications of an independent research study. This editorial does not represent the opinions of the original authors.

Self-assessment scales provide insight into everyday experiences and perceptions of hearing impaired individuals making them valuable companions to laboratory research and helpful tools for clinicians.  A variety of self-assessment indices are available for use with aided or unaided individuals and target a variety of issues including hearing aid usage patterns, binaural or monaural preference, volume and program preferences, ability to understand speech in quiet and noise, and ability to function in social situations.  Gatehouse and Noble point out that most laboratory research and self-assessment scales view speech perception as the primary issue related to hearing handicap, with improved audibility and suppression of competing noise being the primary goal of auditory rehabilitation. But in everyday life, understanding speech may constitute only part of a hearing-impaired individual’s perceived difficulties.  For instance, it is important to locate and identify audible events in order to be fully aware of the environment and safely navigate a variety of surroundings. With the development of the SSQ, Gatehouse and Noble hoped to provide a more comprehensive measure of hearing disability, taking into account the perception of both spatial relationships and sound quality. Furthermore, they investigated the relationship between disabilities in these areas to perceived hearing handicap.

Research regarding auditory scene analysis by Bregman (1990) indicates that a listener in a group situation must first parse the complex acoustic environment into sound sources or “streams” so that they can be attended to and monitored individually. In other words, in a noisy situation, a listener must be able to group together the acoustic elements that make up one particular voice before processing the content of the message. Although it would be easier if it did, conversation rarely proceeds in an orderly fashion with one participant speaking at a time. Rather, in groups, one participant might initiate a response while the previous person is still speaking, or two individuals might speak at the same time. This requires a listener to not only attend to specific speech streams, but to monitor other speech sources in order to be ready to switch attention when necessary.  Accomplishing this task involves binaural hearing, localization, attention, cognition, and vision, and successful communication in groups can be affected by all of these variables. Because the SSQ investigates auditory perceptions of movement, location, and distance as well as sound quality perceptions, such as mood and voice identification in addition to issues related to speech communication, it may more realistically address how hearing loss affects an individual’s everyday life.

The goal of Gatehouse and Noble’s study was twofold: to use the SSQ to examine what is disabling about hearing impairment and to determine how those disabilities affect hearing handicap. There were 153 participants in the study: 80 females and 73 males, with an average age of 71 years. The better-ear average (BEA) for octave frequencies from 500 to 4000Hz was 38.8dB.  The worse-ear average (WEA) was 52.7dB. In addition to the SSQ, subjects completed a 12-question hearing handicap scale developed in part from the Hearing Disabilities and Handicaps Scale (Hetu et al., 1994) and from an unpublished general health scale (Glasgow Health Status Inventory). The items were scored using a 5-point scale, yielding a global handicap score. A higher score indicated greater handicap. Negative scores on the SSQ indicate greater disability, so negative correlations between the SSQ and handicap scores were expected.

The SSQ was designed to be administered as an interview rather than as a self-administered scale. The interview format ensures that the subject understands the questions and can request clarification when necessary. The scale is divided into three domains: 14 items on speech hearing, 17 items on spatial hearing, and 18 items on “other” functions and qualities of hearing. The “other” qualities section contains items related to recognition and segregation of sounds, clarity, naturalness, and listening effort.  Items are scored with ratings of 1 to 10, with the most positive response always represented with a higher number, on the right side of the response sheet. For example, the left side of the scale represents a complete absence of a quality, complete inability to perform a task, or complete effort required. The right side of the scale indicates complete presence of a quality, complete ability, or complete absence of effort.  The left to right, negative-to-positive scoring of items was consistently maintained throughout the scale in an effort to minimize confusion.

They found that degree of hearing impairment correlated well with disability as measured by the SSQ and that the SSQ scores in turn correlated well with handicap, but that impairment itself did not correlate well with handicap. This result was expected and was in agreement with previous research. Asymmetry of hearing loss was not correlated significantly with items in the speech-hearing domain, but did correlate strongly with spatial-hearing and “other” quality domain items such as ease of listening, clarity, and sound segregation.

Examination of SSQ scores within the speech hearing domain showed that the highest ratings were given for one-to-one conversation in quiet. The lowest ratings were for group conversations and contexts in which attention must be divided among two or more sound sources simultaneously.  In the spatial hearing domain, respondents generally rated their directional hearing ability higher than the ability to judge distance or movement. For the “other” qualities domain, items related to naturalness of one’s own voice, recognition of the mood of others from their voices, and recognition of music had the highest scores and those related to ease of listening had the lowest scores.

Following examination of the SSQ scores themselves, the individual items within each of the three SSQ domains were ranked according to the strength of their correlation with hearing handicap. Within the speech-hearing domain, hearing handicap was most influenced by disability in contexts requiring divided or rapidly shifting attention: conversation in a group of people, following two conversations at once, and missing the start of what the next speaker says.  However, handicap was also influenced by difficulty talking to one person in quiet conditions. It is not surprising that a person who perceives difficulty understanding speech in relatively favorable conditions would experience greater concern about their overall communication ability.  Difficulty understanding conversation in noisy situations can be externalized or blamed on the environmental conditions, whereas difficulty in quiet is likely to be internalized and attributed to one’s own disability.

Interestingly, many items in the spatial-hearing domain were as highly correlated with handicap as those within the speech-hearing domain. Questions related to determining the distance and paths of movement, the distance of vehicles, the direction of a barking dog, and locating a speaker in a group setting all contributed to perceived handicap. This underscores the importance of spatial hearing for environmental awareness as well as successful participation in conversation and suggests that examination of spatial hearing may help clinicians and researchers better understand an individual’s experience with their hearing loss.

Several of the items in the “other” qualities section of the SSQ were strongly correlated with handicap. The ability to identify a speaker, to judge a speaker’s mood, the clarity and naturalness of sound, and the effort needed to engage in conversation were among the items most strongly related to hearing handicap.  The authors explain that these abilities affect an individual’s sense of social competence. Failure to accurately interpret the identity or mood of a speaker or the need for increased effort to participate in conversation may have an isolating effect, causing an individual to avoid social situations or even telephone conversations because they fear they will be unable to participate fully or successfully.

Not surprisingly, Gatehouse and Noble found that hearing thresholds were related to SSQ disability scores and SSQ scores were related to handicap, but impairment itself was not strongly correlated to handicap. This finding was expected and is in agreement with previous reports (Hetu et al., 1994). The relationship between impairment, disability, and handicap is important and is familiar to audiologists, in that we routinely discuss how a patient’s hearing loss affects his or her activities and everyday lifestyle. Though consideration of the audiogram is of course important, the way hearing loss interacts with work-related and social activities – things a person must do or enjoys doing  - more likely determines their perceived handicap and therefore their motivation to pursue auditory rehabilitation.

The finding that spatial hearing disability was strongly correlated with handicap may have implications for asymmetric hearing loss as well as the fitting of bilateral hearing aids. Individuals with asymmetric hearing thresholds will have more difficulty localizing sound and therefore may experience more of a handicap related to the discrimination of auditory spatial relationships and movement.  For instance, an individual with asymmetric hearing loss might hear conversation easily but might experience stress because they are unable to judge the location or approach of a car that is not visible. Because individuals with a better or normal ear might rate their speech discrimination performance relatively well in quiet and even moderately noisy places, an assessment scale that examines only speech-related hearing disability might underestimate their perceived hearing handicap. Consideration of spatial hearing deficits might therefore provide a more realistic and helpful assessment of an individual’s functional difficulties. Perception of auditory spatial relationships is likely to be improved with the use of bilateral hearing aids for individuals with binaural hearing loss, so the correlation between spatial hearing items on the SSQ to hearing handicap may also be viewed as further support for the recommendation of two hearing aids.

The correlations across the three domains of the SSQ to the scores on the handicap scale indicate that the SSQ is effectively addressing several variables that contribute to perceived hearing handicap. The impact of speech recognition and discrimination on perceived handicap is well established. The impact of other skills such as determining distance, movement, voice quality, and mood is less well understood but may be an equally important component in understanding an individual’s feelings of social competence and confidence as well as their sense of safety and orientation in a variety of environments. The SSQ provides clinicians and researchers with an additional tool to more fully understand the impact of hearing loss on everyday lives.

References

Bregman, A. (1990). Auditory Scene Analysis: The Perceptual Organization of Sound. Cambridge, MA: MIT Press.

Gatehouse, S. & Noble, W. (2004). The speech, spatial and qualities of hearing scale (SSQ). International Journal of Audiology 43, 85-99.

Hetu, R., Getty, L., Phlibert, L., Desilets, F., Noble, W. (1994). Development of a clinical tool for the measurement of the severity of hearing disabilities and handicaps. Journal of Speech-Language Pathology and Audiology 18, 83-95.

True or False? Two hearing aids are better than one.

McArdle, R., Killion, M., Mennite, M. & Chisolm, T. (2012).  Are Two Ears Not Better Than One? Journal of the American Academy of Audiology 23, 171-181.

This editorial discusses the clinical implications of an independent research study. This editorial does not represent the opinions of the original authors.

Audiologists are accustomed to recommending two hearing aids for individuals with bilateral hearing loss, based on the known benefits of binaural listening (Carhart, 1946; Keys, 1947; Hirsh, 1948; Koenig, 1950), though the potential advantages of binaural versus monaural amplification have been debated for many years.

One benefit of binaural listening, binaural squelch, occurs when the signal and competing noise come from different directions (Kock, 1950; Carhart, 1965). When the noise and signal come from different directions, time and intensity differences cause the waveforms arriving at each ear to be different, resulting in a dichotic listening situation. The central auditory system is thought to combine these two disparate waveforms and essentially subtract the waveform arriving at one side from that of the other, resulting in an effective SNR improvement of about 2-3dB (Dillon, 2001).

Binaural redundancy, another potential benefit of listening with two ears, is an advantage created simply by receiving similar information in both ears. Dillon (2001) describes binaural redundancy as allowing the brain to get two “looks” at the same sound, resulting in SNR improvement of another 1-2 dB (MacKeith & Coles, 1971; Bronkhorst & Plomp, 1988).

Though the benefits of binaural listening would imply benefits of binaural amplification as well, there has been a lack of consensus among researchers. Some studies have reported clear advantages to binaural amplification over monaural fittings, but others have not. Decades ago a number of studies were published on both sides of the argument, but differences in outcomes may have been related to speaker location and the presentation angles of the speech and noise signals (Ross, 1980) so the potential advantages of binaural amplification were still unclear.

Some recent reports have supported the use of monaural amplification over binaural for some individuals, in objective and subjective studies. Henkin et al. (2007) reported that 71% of their subjects performed better on a speech-in-noise task when fitted with one hearing aid on the “better” ear than when fitted with two hearing aids. Cox et al. (2011) reported that 46% of their subjects preferred to use one hearing aid rather than two.

In contrast, a report by Mencher & Davis (2006) concluded that 90% of adults perform better with two hearing aids. They explained that 10% of adults may have experienced negative binaural interaction or binaural interference, which is described as the inappropriate fusion of signals received at the two ears (Jerger et al., 1993; Chmiel et al., 1997).

The phenomenon of binaural interference and the potential advantage of monaural amplification was investigated by Walden & Walden (2005). In a speech recognition in noise task in which speech and the competing babble were presented through a single loudspeaker at 0-degrees azimuth, they found that performance with one hearing aid was better than binaural for 82% of their participants. This is in contrast to Jerger’s (1993) report of an incidence of 8-10% for subjects that might have experienced binaural interference. One criticism of Walden & Walden’s study is that their “monaural” condition left the unaided ear open. Their presentation level of 70dB HL and the use of subjects with mild to moderate hearing loss indicates that subjects were still receiving speech and noise cues in the unaided ear, resulting in an albeit modified, binaural listening situation. Furthermore, their choice of one single loudspeaker for presentation of noise and speech directly in front of the listener created a diotic listening condition, which eliminated the use of binaural head shadow cues. This methodology may have limited their study’s relevance to typical everyday situations in which listeners are engaged in face to face conversation with competing noise all around.

Because the potential advantages or disadvantages of binaural amplification have such important clinical implications, Rachel McArdle and her colleagues sought to clarify the issue with a two-part study of monaural and binaural listening. The first experiment was an effort to replicate Walden and Walden’s 2005 sound field study, this time adding a true monaural condition and an unaided condition. The second experiment examined monaural versus diotic and dichotic listening conditions, using real-world recordings from a busy restaurant.

Twenty male subjects were recruited from the Bay Pines Veteran’s Affairs Medical Facility. Subjects ranged in age from 59 to 85 years old and had bilateral, symmetrical hearing losses. All were experienced users of binaural hearing aids.

For the first experiment, subjects wore their own hearing aids, so a variety of models from different manufacturers were represented. Hearing aids were fitted according to NAL-NL1 prescriptive targets and were verified with real-ear measurements. All of the hearing aids were multi-channel instruments with directional microphones, noise reduction and feedback management. None of the special features were disabled during the study.

Subjects were tested in sound field, with a single loudspeaker positioned 3 feet in front of them. They were tested under five conditions: 1) right ear aided, left ear open, 2) left ear aided, right ear open, 3) binaurally aided, 4) right ear aided, left ear plugged (true monaural) and 5) unaided. The QuickSIN test (Killion et al, 2004) was used to evaluate sentence recognition in noise in all of these conditions. The QuickSIN test yields a value for “SNR loss”, which represents the SNR required to obtain a score of 50% correct for key words in the sentences.

The primary question of interest for the first experiment asked whether two aided ears would achieve better performance than one aided ear. The results showed that only 20% of the participants performed better with one aid, whereas 80% performed better with binaural aids. The lowest SNR loss values were for the binaural condition, followed by right ear aided, left ear aided, true monaural (with left ear plugged) and unaided. Analysis of variance revealed that the binaural condition was significantly better than all other conditions. The right-ear only condition was significantly better than unaided, but all other comparisons failed to reach significance.

The results of Experiment 1 are comparable to results reported by Jerger (1993) but contrast sharply with Walden and Walden’s 2005 study, in which 82% of respondents performed better monaurally aided.  To compare their results further to Walden and Walden’s, McArdle and her colleagues compiled scores for the subjects’ better ears and found that there was no significant difference between binaural and better ear performance, but both of these conditions were significantly better than the other conditions. They also examined the effect of degree of hearing loss and found that individuals with hearing thresholds poorer than 70dB HL were able to achieve about twice as much improvement from binaural amplification as those subjects with better hearing. Still, the results of Experiment 1 support the benefit of binaural hearing aids for most participants, especially those with poorer hearing.

The purpose of Experiment 2 was to further examine the potential benefit of hearing with two ears, using diotic and dichotic listening conditions. Diotic listening refers to a condition in which the listener receives the same stimulus in both ears, whereas dichotic listening refers to more typical real-world conditions in which each ear receives slightly different information, subject to head shadow and time and intensity differences.

Speech recognition was evaluated in four conditions: 1) monaural right, 2) monaural left, 3) diotic and 4) binaural or dichotic. Materials for the R-SPACE QSIN test (Revit, et al., 2007) were recorded through a KEMAR manikin with competing restaurant noise presented through eight loudspeakers. Recordings were taken from eardrum-position microphones on each side of KEMAR, thus preserving binaural cues that would be typical for a listener in a real-world setting.

In Experiment 2, subjects were not tested wearing hearing aids; the stimuli were presented via insert earphones. The use of recorded stimuli presented under earphones eliminated the potentially confounding factor of hearing aid technology on performance and allowed the presentation of real-world recordings in truly monaural, diotic and dichotic conditions.

The best performance was demonstrated in the binaural condition, followed by the diotic condition, then the monaural conditions. The binaural condition was significantly better than diotic and both the diotic and dichotic conditions were significantly better than the monaural conditions. Again in contrast to Walden and Walden’s study, 80% of the subjects scored better in the binaural condition than either of the monaural conditions and 65% of the subjects scored better in the diotic condition than either monaural condition. These results support the findings of the first experiment and indicate that for the majority of listeners, speech recognition in noise improves when two ears are listening instead of one. Furthermore, the finding that the binaural condition was significantly better than the diotic condition indicates that it is not only the use of two ears, but also the availability of binaural cues that have a positive impact on speech recognition in competing noise.

McArdle and her colleagues point out that their study, as well as other recent reports (Walden & Walden, 2005; Henkin, 2007), suggests that the majority of listeners perform better on speech-in-noise tasks when they are listening with two ears. When binaural time and intensity cues are available, performance is even better than with the same stimulus reaching each ear.  They also found that the potential benefit of binaural hearing was even more pronounced for individuals with more severe hearing loss. This supports the recommendation of binaural hearing aids for individuals with bilateral hearing loss, especially those with severe loss.

Cox et al (2011) reported that listeners who experienced better performance in everyday situations tended to prefer binaural hearing aid use, but also found that 43 out of 94 participants generally preferred monaural to binaural use over a 12-week trial. For new hearing aid users or prior monaural users, this is not surprising, as it can take time to adjust to binaural hearing aid use. Clinical observation suggests that individuals who have prior monaural hearing aid experience may have more difficulty adjusting to binaural use than individuals who are new to hearing aids altogether.  However, with consistent daily use, reasonable expectations and appropriate counseling, most users can successfully adapt to binaural use. It is possible that the subjects in Cox et al’s study who preferred monaural use were responding to factors other than performance in noise. If they were switching between monaural and binaural use, perhaps they did not wear the two instruments together consistently enough to fully acclimate to binaural use in the time allotted.

Though their study presented strong support for binaural hearing aid use, McArdle and her colleagues suggest that listeners may benefit from “self-experimentation” to determine the optimal configuration with their hearing aids. This suggestion is an excellent one, but it may be most helpful within the context of binaural use. Even patients with adaptive and automatic programs can be fitted with manually accessible programs designed for particularly challenging situations and should be encouraged to experiment with these programs to determine the optimal settings for their various listening needs.

Clinicians who have been practicing for several years may recall the days when hearing aid users often lost their hearing aids in restaurants because they had removed one aid in order to more easily ignore background noise. That is less likely to occur now, as current technology can help most hearing aid users function quite well in noisy situations. With directional microphones and multiple programs, along with the likelihood that speech and background noise are often spatially separated, binaural hearing aids are likely to offer advantageous performance for speech recognition in most acoustic environments. Bilateral data exchange and wireless communication offer additional binaural benefits, as two hearing instruments can work together to improve performance in noise and provide binaural listening for telephone or television use.

References

Bronkhorst, A.W. & Plomp, R. (1988). The effect of head induced interaural time and level differences on speech intelligibility in noise. Journal of the Acoustical Society of America 83, 1508-1516.

Carhart, R. (1965). Problems in the measurement of speech discrimination. Archives of Otolaryngology 82, 253-260.

Carhart, R. (1946). Selection of hearing aids. Archives of Otolaryngology 44, 1-18.

Chmiel, R., Jerger, J., Murphy, E., Pirozzolo, R. & Tooley, Y.C. (1997). Unsuccessful use of binaural amplification by an elderly person. Journal of the American Academy of Audiology 8, 1-10.

Cox, R.M., Schwartz, K.S., Noe, C.M. & Alexander, G.C. (2011). Preference for one or two hearing aids among adult patients. Ear and Hearing 32 (2), 181-197.

Dillon, H. (2001). Monaural and binaural considerations in hearing aid fitting. In: Dillon, H., ed. Hearing Aids. Turramurra, Australia: Boomerang Press, 370-403.

Henkin, Y., Waldman, A. & Kishon-Rabin, L. (2007). The benefits of bilateral versus unilateral amplification for the elderly: are two always better than one? Journal of Basic and Clinical Physiology and Pharmacology 18(3), 201-216.

Hirsh, I.J. (1948). Binaural summation and interaural inhibition as a function of the level of masking noise. American Journal of Psychology 61, 205-213.

Jerger, J., Silman, S., Lew, J. & Chmiel, R. (1993). Case studies in binaural interference: converging evidence from behavioral and electrophysiologic measures. Journal of the American Academy of Audiology 4, 122-131.

Keys, J.W. (1947). Binaural versus monaural hearing. Journal of the Acoustical Society of America 19, 629-631.

Killion, M.C., Niquette, P.A., Gudmundsen, G.I., Revit, L.J. & Banerjee, S. (2004). Development of a quick speech-in-noise test for measuring signal-to-noise ratio loss in normal hearing and hearing-impaired listeners. Journal of the Acoustical Society of America 116, 2395-2405.

Kock, W.E. (1950). Binaural localization and masking. Journal of the Acoustical Society of America 22, 801-804.

Koenig, W. (1950). Subjective effects in binaural hearing. [Letter to the Editor] Journal of the Acoustical Society of America 22, 61-62.

MacKeith, N.W. & Coles, R.A. (1971). Binaural advantages in hearing speech. Journal of Laryngology and Otology 85, 213-232.

McArdle, R., Killion, M., Mennite, M. & Chisolm, T. (2012).  Are Two Ears Not Better Than One? Journal of the American Academy of Audiology 23, 171-181.

Mencher, G.T. & Davis, A. (2006) Binaural or monaural amplification: is there a difference? A brief tutorial. International Journal of Audiology 45, S3-S11.

Revit, L., Killion, M. & Compton-Conley, C. (2007). Developing and testing a laboratory sound system that yields accurate real-world results. Hearing Review online edition, www.hearingreview.com, October 2007.

Ross, M. (1980). Binaural versus monaural hearing aid amplification for hearing impaired individuals. In: Libby, E.R., Ed. Binaural Hearing and Amplification. Chicago: Zenetron, 1-21.

Walden, T.C. & Walden, B.E. (2005). Monaural versus binaural amplification for adults with impaired hearing. Journal of the American Academy of Audiology 16: 574-584.

Do Patients with Severe Hearing Loss Benefit from Directional Microphones?

Ricketts, T.A., & Hornsby, B.W.Y. (2006). Directional hearing aid benefit in listeners with severe hearing loss. International Journal of Audiology, 45, 190-197.

This editorial discusses the clinical implications of an independent research study. The original work was not associated with Starkey Hearing Technologies. This editorial does not represent the opinions of the original authors.

The benefit of directional microphones for speech recognition in noise is well established for individuals with mild to moderate hearing loss (Madison & Hawkins, 1983; Killion et al., 1998; Ricketts 2000a; Ricketts & Henry, 2002).  The potential benefit of directional microphones for severely hearing-impaired individuals is less understood and few studies have examined directional benefit when hearing loss is greater than 65dB.

Killion and Christensen (1998) proposed that listeners with severe-to-profound hearing loss may experience reduced directional benefit because they are less able to make use of speech information across frequencies. Ricketts, Henry and Hornsby confirmed this hypothesis in a 2005 study. They found an approximately 7% increase in speech recognition score per 1dB increase in directivity for listeners with moderate hearing loss, whereas listeners with severe loss achieved only an approximately 3.5% increase per 1dB increase in directivity.

In their 2005 study, Ricketts and Hornsby used individually determined SNRs and auditory-visual stimuli that allowed testing at poorer SNRs without floor effects. The authors point out that visual cues usually offer a greater benefit at poor SNRs, especially for sentence materials (Erber, 1969; Sumby & Pollack, 1954; MacLeod & Summerfield, 1987).  Individuals rely more on visual cues in poorer SNRs, visual information that provides complementary, non-redundant cues is most beneficial (Grant, 1998; Walden et al., 1993).

The purpose of their study was to examine potential directional benefit for severely hearing-impaired listeners at multiple SNRs in auditory-only and auditory-visual conditions. Directional and omnidirectional performance in quiet conditions were also tested to rule out performance differences between microphone modes that could be attributed to reduction of environmental noise by the directional microphone. Finally, it was determined if performance in quiet conditions would significantly exceed performance in highly positive SNRs. Though significant improvement in SNRs more favorable than +15 dB is usually not expected, some research suggests that hearing-impaired individuals may experience additional benefit from more favorable SNRs (Studebaker et al, 1999).

Twenty adult participants with severe-to-profound sensorineural hearing loss participated in the study. All participants used oral communication, had at least nine years of experience with hearing aids and had pure tone average hearing thresholds greater than 65dB.  Participants were fitted with power behind-the-ear hearing aids with full shell, unvented earmolds. Digital noise reduction and feedback management was turned off. The directional program was equalized, so that gain matched the omnidirectional mode as closely as possible.

The Audio/Visual Connected Speech Test (CST; Cox et al, 1987), a speech recognition test with paired passages of connected speech, was presented to listeners on DVD. Speech was presented at a 0-degree azimuth angle and uncorrelated competing noise was presented via five loudspeakers surrounding the listener. Testing took place in a sound booth with reflective panels to approximate common levels of reverberation in everyday situations.

Baseline SNRs were obtained for each subject in auditory-only and auditory-visual conditions, at a level that was near, but not reaching floor performance. Speech recognition testing was conducted for omnidirectional and directional conditions at baseline SNR, baseline + 4dB and baseline + 8dB. Presentation SNRs ranged from 0dB to +24dB for auditory-only conditions and from -6dB to +18dB for auditory-visual conditions. Listeners were tested with auditory-only stimuli in quiet conditions, for omnidirectional and directional modes. Testing in quiet was not performed with auditory-visual stimuli, as performance was expected to approach ceiling performance levels.

The multiple SNR levels were achieved with two different methodologies. Half of the participants listened to a fixed noise level of 60dB SPL and speech levels were varied to achieve the desired SNRs. The remaining participants listened to a fixed speech level of 67dB SPL and the noise levels were adjusted to reach the desired SNR levels. Data analysis revealed no significant differences between these two test methodologies for any of the variables, so their data was pooled for subsequent analyses.

The results showed significant main effects for microphone mode (directional versus omni), SNR and presentation condition (auditory-only versus auditory-visual). There were significant interactions between microphone mode and SNR, as well as between presentation condition and SNR.  Each increase in SNR resulted in significantly better performance for both omnidirectional and directional modes. Performance in directional mode was significantly better than omnidirectional for all SNR levels. The authors pointed out that auditory-visual performance at all three SNRs was always better than auditory-only, despite the fact that the absolute SNRs for auditory-visual conditions were lower than the equivalent auditory-only conditions, by an average of 5dB.  The authors interpreted this finding as strong support for the benefit of visual cues for speech recognition in adverse conditions.

When the effects of directionality and SNR were analyzed separately for auditory-only and auditory-visual conditions, they found that directional performance was significantly better than omnidirectional performance for all auditory-visual conditions. In auditory-only conditions, directionality only had a significant effect at the baseline SNR, but not in the baseline +4dB, baseline +8dB or quiet conditions.

Perhaps not surprisingly, Ricketts and his colleagues found that the addition of visual cues offered their severely-impaired listeners a significant advantage for understanding connected speech. When they compared the auditory-only and auditory-visual scores at equivalent SNR levels, they determined that participants achieved an average improvement of 22% with the availability of visual cues. This finding is in agreement with previous research that found a visual advantage of 24% for listeners with moderate hearing loss (Henry & Ricketts, 2003).

Also not surprisingly, performance improved with increases in signal to noise ratio.  For the auditory-only condition, they found an average improvement of 1.6% per dB and 2.7% per dB for the omnidirectional and directional modes, respectively. For the auditory-visual condition, there was an improvement of 3.7% per dB for omnidirectional mode and 3.1% per dB for directional mode.  Furthermore, they found an additional performance increase of 8% for directional mode and 12% for omnidirectional mode when participants were tested in quiet conditions. This was somewhat surprising given previous research based on the articulation index (AI) that suggested maximal performance could be expected at SNRs of approximately +15dB.  The absolute SNR for the baseline +8dB condition was 14.7dB, so further improvements in quiet conditions support the suggestion that hearing-impaired listeners experience increased improvement for SNRs up to +20dB (Studebaker et al, 1999; Sherbecoe & Studebaker, 2002).

The benefit of visual cues was not specifically addressed by this study because it did not compare auditory-only and auditory-visual performance at the same SNR levels. However, the discovery that visual cues improved performance even when the SNRs were approximately 5dB poorer was strong support for the benefit of visual information for speech recognition in noisy environments. This underscores the recommendation that severely hearing-impaired listeners should always be counseled to take advantage of visual cues whenever possible, especially in adverse listening conditions. Although visual cues cannot completely counterbalance the auditory cues lost to hearing loss and competing noise, they supply additional information that can help the listener identify or differentiate phonemes, especially in connected speech containing semantic and syntactic context. In conversational situations, visual cues include not just lip-reading but also the speaker’s gestures, expressions and body language. All of these cues can aid speech recognition, so hearing-impaired individuals as well as their family members should be trained in strategies to maximize the availability of visual information.

Ricketts and Hornsby’s study supports the potential benefit of directional microphones for individuals with severe hearing loss. Many hearing aid users with severe-to-profound loss have become accustomed to the use of omnidirectional microphones and may be resistant to directional microphones, especially automatic directionality, if it is in the primary program of their hearing instruments. One strategy for addressing these cases is to program the hearing aid’s primary memory as full-time omnidirectional while programming a second, manually accessed, memory with a full-time directional microphone. This way the listener is able to choose when and how they use their directional program and may be less likely to experience unexpected and potentially disconcerting changes in perceived loudness and sound quality.

In addition to providing evidence for the benefit of visual cues and directionality, the findings of this study can be extrapolated to support the use of FM and wireless accessories. The fact that performance in quiet conditions was still significantly better than the next most favorable SNR (14.7dB) shows that improving SNR as much as possible provides demonstrable advantages for listeners with severe hearing loss. Even for individuals who do well with their hearing instruments overall, wireless accessories that stream audio directly to the listeners hearing instruments may further improve understanding. These accessories improve SNR by reducing the effect of room acoustics and reverberation, as well as reducing the effect of competing noise and distance between the sound source and the listener. Most modern hearing instruments are compatible with wireless accessories so hearing aid evaluations should always include discussion of their potential benefits. These devices work with a wide range of hearing aid styles, do not require the use of an adapter or receiver boot and are much less expensive than an FM system.

Ricketts and Hornsby’s study underscores the importance of visual information and directionality for speech recognition in noisy environments and illuminates ways in which clinicians can help patients with severe-to-profound loss achieve improved communication in everyday circumstances. Modern technologies such as directional processing and wireless audio streaming accessories can be effective tools for improving SNRs in everyday situations that may otherwise challenge or overwhelm the listener with severe to profound hearing loss.

References

Erber, N.P. (1969). Interaction of audition and vision in the reception of oral speech stimuli. Journal of Speech and Hearing Research 12, 423-425.

Grant, K.W., Walden, B.E. & Seitz, P.F. (1998). Auditory-visual speech recognition by hearing-impaired subjects: consonant recognition, sentence recognition and auditory-visual integration. Journal of the Acoustical Society of America 103, 2677-2690.

Henry, P. & Ricketts, T. A. (2003).  The effect of head angle on auditory and visual input for directional and omnidirectional hearing aids. American Journal of Audiology 12(1), 41-51.

Killion, M. C., Schulien, R., Christensen, L., Fabry, D. & Revit, L. (1998). Real world performance of an ITE directional microphone. Hearing Journal 51(4), 24-38.

Killion, M.C. & Christensen, L. (1998). The case of the missing dots: AI and SNR loss. Hearing Journal 51(5), 32-47.

MacLeod, A. & Summerfield, Q. (1987). Quantifying the contribution of vision to speech perception in noise. British Journal of Audiology 21, 131-141.

Madison, T.K. & Hawkins, D.B. (1983). The signal-to-noise ratio advantage of directional microphones. Hearing Instruments 34(2), 18, 49.

Pavlovic, C. (1984). Use of the articulation index for assessing residual auditory function in listeners with sensorineural hearing impairment. Journal of the Acoustical Society of America 75, 1253-1258.

Pavlovic, C., Studebaker, G. & Scherbecoe, R. (1986). An articulation index based procedure for predicting the speech recognition performance of hearing-impaired individuals. Journal of the Acoustical Society of America 80(1), 50-57.

Ricketts, T.A. (2000a). Impact of noise source configuration on dire3ctional hearing aid benefit and performance. Ear and Hearing 21(3), 194-205.

Ricketts, T.A. & Henry, P. (2002). Evaluation of an adaptive directional microphone hearing aid. International Journal of Audiology 41(2), 100-112.

Ricketts, T., Henry, P. & Hornsby, B. (2005). Application of frequency importance functions to directivity for prediction of benefit in uniform fields. Ear & Hearing 26(5), 473-86.

Studebaker, G., Sherbecoe, R., McDaniel, D. & Gwaltney, C. (1999). Monosyllabic word recognition at higher-than-normal speech and noise levels. Journal of the Acoustical Society of America 105(4), 2431-2444.

Sherbecoe, R.L., Studebaker, G.A. (2002). Audibility-index functions for the Connected Speech Test. Ear & Hearing 23(5), 385-398.

Sumby, W.H. & Pollack, I. (1954). Visual contribution to speech intelligibility in noise. Journal of the Acoustical Society of America 26, 212-215.

Walden, B.E., Busacco, D.A. & Montgomery, A.A. (1993). Benefit from visual cues in auditory-visual speech recognition by middle-aged and elderly persons. Journal of Speech and Hearing Research 36, 431-436.