Starkey Research & Clinical Blog

Addressing patient complaints when fine-tuning a hearing aid

Jenstad, L.M., Van Tasell, D.J. & Ewert, C. (2003). Hearing aid troubleshooting based on patient’s descriptions. Journal of the American Academy of Audiology 14 (7).

This editorial discusses the clinical implications of an independent research study. The original work was not associated with Starkey Laboratories and does not reflect the opinions of the authors.

As part of any clinically robust protocol, a hearing aid fitting will be objectively verified with real-ear measures and validated with a speech-in-noise test. Fine tuning and follow-up adjustments are an equally important part of the fitting process. This stage of the routine fitting process does not follow standardized procedures and is almost always directed by a patient’s complaints or descriptions of real-world experience with the hearing aids. This can be a challenging dynamic for the clinician. Patients may have difficulty putting their auditory experience into words and different people may describe similar sound quality issues in different ways.  Additionally, there may be several ways to address any given complaint and a given programming adjustment may not have the same effect on different hearing aids.

Hearing aid manufacturers often include a fine-tuning guide or automated fitting assistant within their software to help the clinician make appropriate adjustments for common patient complaints. There are limitations to the effectiveness of these fine tuning guides in that they are inherently specific to a limited range of products and the suggested adjustments are subject to the expertise and resources of that manufacturer.  The manner in which a sound quality complaint is described may differ between manufacturers and the recommended adjustments in response to the complaint may differ as well.

There have been a number of efforts to develop a single hearing aid troubleshooting guide that could be used across devices and manufacturers (Moore et. al., 1998; Gabrielsson et al., 1979, 1988, 1990; Lundberg et al., 1992; Ovegard et al., 1997). The first and perhaps most challenging step toward this goal has been to determine the most common descriptors that patients use for sound quality complaints. Moore (1998) and his colleagues developed a procedure in which responses on three ratings scales (e.g., “loud versus quiet”, “tinny versus boomy”) were used to make adjustments to gain and compression settings. However, their procedure did not allow for the bevy of descriptors that patients create; limiting potential utility for everyday clinical settings.  Gabrielsson colleagues, in a series of Swedish studies, developed a set of reliable terms to describe sound quality. These descriptors have since been translated and used in English language research (Bentler et al., 1993).

As hearing instruments become more complicated with numerous adjustable parameters, and given the wide range of experience and expertise of individuals fitting hearing instruments today, an independent fine tuning guide is an appealing concept. Lorienne Jenstad and her colleagues proposed an “expert system” for troubleshooting hearing aid complaints.  The authors explained that expert systems “emulate the decision making abilities of human experts” (Tharpe et al., 1993).  To develop the system, two primary questions were asked:

1) What terms do hearing impaired listeners use to describe their reactions to specific hearing aid fitting problems?

2) What is the expert consensus on how these patient complaints can be addressed by hearing aid adjustment?

There were two phases to the project. To address question one, the authors surveyed clinicians for their reports on how patients describe sound quality with regard to specific fitting problems. To address question two, the most frequently reported descriptors from the clinicians’ responses were submitted to a panel of experts to determine how they would address the complaints.

The authors sent surveys to 1934 American Academy of Audiology members and received 311 qualifying responses. The surveys listed 18 open-ended questions designed to elicit descriptive terms that patients would likely use for hearing aid fitting problems. For example, the question “If the fitting has too much low-frequency gain…” yielded responses such as “hollow”, “plugged” and “echo”.  The questions probed common problems related to gain, maximum output, compression, physical fit, distortion and feedback.  The survey responses yielded a list of the 40 most frequent descriptors of hearing aid fitting problems, ranked according to the number of occurrences.

The list of descriptors was used to develop a questionnaire to probe potential solutions for each problem.  Each descriptor was put in the context of, “How would you change the fitting if your patient reports that ___?”, and 23 possible fitting solutions were listed.  These questionnaires were completed by a panel of experts with a minimum of five years of clinical experience. Respondents could offer more than one solution to a problem and the solutions were weighted based on the order in which they were offered. There was strong agreement among experts, suggesting that their responses could be used reliably to provide troubleshooting solutions based on sound quality descriptions. The expert responses also agreed with the initial survey that was sent to the group of 1934 audiologists, supporting the validity of these response sets.

The expert responses resulted in a fine-tuning guide in the form of tables or simplified flow charts. The charts list individual descriptors with potential solutions listed below in the order in which they should be attempted.  For example, below the descriptor “My ear feels plugged”, the first solution is to “increase vent” and the second is to “decrease low frequency gain”. The idea is that the clinician would first try to increase the vent diameter and if that didn’t solve the problem, they would move on to the second option, decreasing low frequency gain. If an attempted solution creates another sound quality problem, the table can be utilized to address that problem in the same way.

The authors correctly point out that there are limitations to this tool and that proposed solutions will not necessarily have the same results with all hearing aids. For instance, depending on the compressor characteristics, raising a kneepoint might increase OR decrease the gain at input levels below the kneepoint. It is up to the clinician to be familiar with a given hearing aid and its adjustable parameters to arrive at the appropriate course of action.

Beyond manipulation of the hearing aid itself, the optimal solution for a particular patient complaint might not be the first recommendation in any tuning guide. For instance, for the fitting problem labeled “Hearing aid is whistling”, the fourth solution listed in the table is “check for cerumen”.  This solution appeared fourth in the ranking based on the frequency of responses from the experts on the panel. However, any competent clinician who encounters a patient with hearing aid feedback should check for cerumen first before considering programming modifications.

The expert system proposed by Jenstad and her colleagues represents a thoroughly examined, reliable step toward development of a universal troubleshooting guide for clinicians. Their paper was published in 2003, so some items should be updated to suit modern hearing aids. For example, current feedback management strategies result in fewer and less challenging feedback problems.  Solutions for feedback complaints might now include, “calibrate feedback management system” versus gain or vent adjustments. Similarly, most hearing aids now have solutions for listening in noise that extend beyond the simple inclusion of directional microphones, so “directional microphone” might not be an appropriately descriptive solution to address complaints about hearing in noise, as the patient is probably already using a directional microphone.

Overall, the expert system proposed by Jenstad and colleagues is a helpful clinical tool; especially if positioned as a guide to help patients find the appropriate terms to describe their perceptions. However, as the authors point out, it is not meant to replace prescriptive methods, measures of verification and validation, or the expertise of the audiologist. The responsibility is with the clinician to be informed about current technology and its implications for real world hearing aid performance and to communicate with their patients in enough detail to understand their patients’ comments and address them appropriately.

References

Bentler, R.A., Nieburh, D.P., Getta, J.P. & Anderson, C.V. ( 1993). Longitudinal study of hearing aid effectiveness II: subjective measures. Journal of Speech and Hearing Research 36, 820-831.

Jenstad, L.M., Van Tasell, D.J. & Ewert, C. (2003). Hearing aid troubleshooting based on patient’s descriptions. Journal of the American Academy of Audiology 14 (7).

Moore, B.C.J., Alcantara, J.I. & Glasberg, B.R. (1998). Development and evaluation of a procedure for fitting multi-channel compression hearing aids. British Journal of Audiology 32, 177-195.

Gabrielsson A. ( 1979). Dimension analyses of perceived sound quality of sound-reproducing systems. Scandinavian Journal of Psychology 20, 159-169.

Gabrielsson, A., Hagerman, B., Bech-Kristensen, T. & Lundberg, G. (1990). Perceived sound quality of reproductions with different frequency responses and sound levels. Journal of the Acoustical Society of America 88, 1359-1366.

Gabrielsson, A. Schenkman, B.N. & Hagerman, B. (1988). The effects of different frequency responses on sound quality judgments and speech intelligibility. Journal of Speech and Hearing Research 31, 166-177.

Lundberg, G., Ovegard, A., Hagerman, B., Gabrielsson, A. & Brandstom, U. (1992). Perceived sound quality in a hearing aid with vented and closed earmold equalized in frequency response. Scandinavian Audiology 21, 87-92.

Ovegard, A., Lundberg, G., Hagerman, B., Gabrielsson, A., Bengtsson, M. & Brandstrom, U. (1997). Sound quality judgments during acclimatization of hearing aids. Scandinavian Audiology 26, 43-51.

Schweitzer, C., Mortz, M. & Vaughan, N. (1999). Perhaps not by prescription – but by perception. High Performance Hearing Solutions 3, 58-62.

Tharpe, A.M., Biswas, G. & Hall, J.W. (1993). Development of an expert system for pediatric auditory brainstem response interpretation. Journal of the American Academy of Audiology 4, 163-171.

Recommendations for fitting patients with cochlear dead regions

Cochlear Dead Regions in Typical Hearing Aid Candidates:

Prevalence and Implications for Use of High-Frequency Speech Cues

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

This editorial discusses the clinical implications of an independent research study. The original work was not associated with Starkey Laboratories and does not reflect the opinions of the authors.

Audibility is a well-known predictor of speech recognition ability (Humes, 2007) and audibility of high-frequency information is of particular importance for consonant identification.  Therefore, audibility of high-frequency speech cues is appropriately regarded as an important element of successful hearing aid fittings (Killion & Tillman, 1982; Skinner & Miller, 1983). In contrast to this expectation, some studies have reported that high-frequency gain might have limited or even negative impact on speech recognition abilities of some individuals (Murray & Byrne, 1986; Ching et al., 1998; Hogan & Turner, 1998). These researchers observed that when high-frequency hearing loss exceeded 55-60dB, some listeners were unable to benefit from increased high-frequency audibility.  A potential explanation for this variability was provided by Brian Moore (2001), who suggested that an inability to benefit from amplification in a particular frequency region could be due to cochlear “dead regions” or regions where there is a loss of inner hair cell functioning.

Moore suggested that hearing aid fittings could potentially be improved if clinicians were able to identify patients with cochlear dead regions (DRs). Working under the assumption that diagnosis DRs may contraindicate high-frequency amplification. He and his colleagues developed the TEN test as a method of determining the presence of cochlear dead regions (Moore et al., 2000, 2004). The advent of the TEN test provided a standardized measurement protocol for DRs, but there is still wide variability in the reported prevalence of DRs. Estimates range from as 29% (Preminger et a., 2005) to as high as 84% (Hornsby & Dundas, 2009), with other studies reporting DR prevalence somewhere in the middle of that range. Several potential factors are likely to contribute to this variability, including degree of hearing loss, audiometric configuration and test technique.

In addition to the variability in reported prevalence of DRs, there is also variability in the reports of how DRs affect the ability to benefit from high-frequency speech cues (Vickers et al., 2001; Baer et al., 2002; Mackersie et al., 2004). It remains unclear as to whether high-frequency amplification recommendations should be modified to reflect the presence of DRs.  Most research is in agreement that as hearing thresholds increase, the likelihood of DRs also increases.  Hearing aid users with severe to profound hearing losses are likely to have at least one DR. Because a large proportion of hearing aid users have moderate to severe hearing losses, Dr. Cox and her colleagues wanted to determine the prevalence of DRs in this population. In addition, they examined the effect of DRs on the use of high-frequency speech cues by individuals with moderate to severe loss.

Their study addressed two primary questions:

1) What is the prevalence of dead regions (DRs) among listeners with hearing thresholds in the 60-90dB range?

2) For individuals with hearing loss in the 60-90dB range, do those with DRs differ from those without DRs in their ability to use high-frequency speech cues?

One hundred and seventy adults with bilateral, flat or sloping sensorineural hearing loss were tested. All subjects had thresholds of 60 to 90dB in the better ear for at least part of the range from 1-3kHz and thresholds no better than 25dB for frequencies below 1kHz. Subjects ranged in age from 38 to 96 years, and 59% of the subjects had experience with hearing aids.

First, subjects were evaluated for the presence of DRs with the TEN test. Then, speech recognition was measured using high-frequency emphasis (HFE) and high-frequency emphasis, low-pass filtered (HFE-LP) stimuli from the QSIN test (Killion et al. 2004). HFE items on this test are amplified up to 32dB above 2.5kHz, whereas the HFE-LP items have much less gain in this range. Comparison of subjects’ responses to these two types of stimuli allowed the investigators to assess changes in speech intelligibility with additional high frequency cues. Presentation levels for the QSIN were chosen by using a loudness scale and bracketing procedure to arrive at a level that the subject considered “loud but okay”. Finally, audibility differences for the two QSIN conditions were estimated using the Speech Intelligibility Index based on ANSI 3.5-1997 (ANSI, 1997).

The TEN test results revealed that 31% of the participants had DRs at one or more test frequencies. Of the 307 ears tested, 23% were found to have a DR for one or more frequencies. Among those who tested positive for DRs, about 1/3 had DRs in both ears and 2/3 had DRs in one ear or the other in equal proportion. Mean audiometric thresholds were essentially identical for the two groups below 1kHz, but above 1kHz thresholds were significantly poorer for the group with DRs than for the group without DRs.  DRs were most prevalent at frequencies above 1.5kHz. There were no age or gender differences.

On the QSIN test, the mean HFE-LP scores were significantly poorer than the mean HFE scores for both groups.  There was also a significant difference in performance based on whether or not the participants had DRs. Perhaps more interestingly, there was a significant interaction between the DR group and test stimuli conditions, in that the additional high-frequency information in the HFE stimuli resulted in slightly greater performance gains for the group without DRs than it did for the group with DRs.  Furthermore, subjects with one or more isolated DRs were more able to benefit from the high frequency cues in the HFE lists than were those subjects with multiple, contiguous DRs. Although there were a few isolated individuals who demonstrated lower scores for the HFE stimuli, the differences were not significant and could have been explained by measurement error. Therefore, the authors conclude that the additional high frequency information in the HFE stimuli was not likely to have had a detrimental effect on performance for these individuals.

As had also been reported in previous studies, subject groups with DRs had poorer mean audiometric thresholds than the groups without DRs, so it was possible that audibility played a role in QSIN performance. Analysis of the audibility of QSIN stimuli for the two groups revealed that high frequency cues in the HFE lists were indeed more audible for the group without DRs. In accounting for this audibility effect, the presence of DRs still had a small but significant effect on performance.

The results of this study suggest that listeners with cochlear DRs still benefit from high frequency speech cues, albeit slightly less than those without dead regions.  The performance improvements were small and the authors caution that it is premature to draw firm conclusions about the clinical implications of this study.  Despite the need for further examination, the results of the current study certainly do not support any reduction in prescribed gain for hearing aid candidates with moderate to severe hearing losses.  The authors acknowledge, however, that because the findings of this and other studies are based on group data, it is possible that specific individuals may be negatively affected by amplification within dead regions. Based on the research to date, this seems more likely to occur in individuals with profound hearing loss who may have multiple, contiguous DRs.

More study is needed to determine the most effective clinical approach to managing cochlear dead regions in hearing aid candidates. Future research should be done with hearing aid users, including for example, the effects of noise on everyday hearing aid performance for individuals with DRs. A study by Mackersie et. al. (2004) showed that subjects with DRs suffered more negatives effects of noise than did the subjects without DRs. If there is a convergence of evidence to this effect, then recommendations about the use of high frequency gain, directionality and noise reduction could be determined as they relate to DRs. For now, Dr. Cox and her colleagues recommend that until there are clear criteria to identify individuals for whom high frequency gain could have deleterious effects, clinicians should continue using best-practice protocols and provide high frequency gain according to current prescriptive methods.

References

ANSI ( 1997). American National Standard Methods for Calculation of the Speech Intelligibility Index (Vol. ANSI S3.5-1997). New York: American National Standards Institute.

Ching,T., Dillon, H. & Byrne, D. (1998). Speech recognition of hearing-impaired listeners: Predictions from audibility and the limited role of high-frequency amplification. Journal of the Acoustical Society of America 103, 1128-1140.

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

Hogan, C.A. & Turner, C.W. (1998). High-frequency audibility: Benefits for hearing-impaired listeners. Journal of the Acoustical Society of America 104, 432-441.

Humes, L.E. (2007). The contributions of audibility and cognitive factors to the benefit provided by amplified speech to older adults. Journal of the American Academy of Audiology 18, 590-603.

Killion, M. C. & Tillman, T.W. (1982). Evaluation of high-fidelity hearing aids. Journal of Speech and Hearing Research 25, 15-25.

Moore, B.C.J. (2001). Dead regions in the cochlear: Diagnosis, perceptual consequences and implications for the fitting of hearing aids. Trends in Amplification 5, 1-34.

Moore, B.C.J., Huss, M., Vickers, D.A.,  et al. (2000). A test for the diagnosis of dead regions in the cochlea. British Journal of Audiology 34, 2-5-224.

Moore, B.C.J., Glasberg, B.R., Stone, M.A. (2004). New version of the TEN test with calibrations in dB HL. Ear and Hearing 25, 478-487.

Murray, N. & Byrne, D. (1986). Performance of hearing-impaired and normal hearing listeners with various high-frequency cut-offs in hearing aids. Australian Journal of Audiology 8, 21-28.

Skinner, M.W. & Miller, J.D. (1983). Amplification bandwidth and intelligibility of speech in quiet and noise for listeners with sensorineural hearing loss.  Audiology 22, 253-279.

A preferred speech stimulus for testing hearing aids

Development and Analysis of an International Speech Test Signal (ISTS)

Holube, I., Fredelake, S., Vlaming, M. & Kollmeier, B. (2010). Development and analysis of an international speech test signal (ISTS). International Journal of Audiology, 49, 891-903.

This editorial discusses the clinical implications of an independent research study. The original work was not associated with Starkey Laboratories and does not reflect the opinions of the authors.

Current hearing aid functional verification measures are described in the standards IEC 60118 and ANSI 3.22 and use stationary signals, including sine wave frequency sweeps and unmodulated noise signals. Test stimuli are presented to the hearing instrument and frequency specific gain and output is measured in a coupler or ear simulator.  Current standardized measurement methods require the instrument to be set at maximum or a reference test setting and adaptive parameters such as noise reduction and feedback management are turned off.

These procedures provide helpful information for quality assurance and determining fitting ranges for specific hearing aid models. However, because they were designed for linear, time-invariant hearing instruments, they have limitations for today’s nonlinear, adaptive instruments and cannot provide meaningful information about real-life performance in the presence of dynamically changing acoustic environments.

Speech is the most important stimulus encountered by hearing aid users and nonlinear hearing aids with adaptive characteristics process speech differently than they do stationary signals like sine waves and unmodulated noise. Therefore, it seems preferable for standardized test procedures to use stimuli that are as close as possible to natural speech.  Indeed, there are some hearing aid test protocols that use samples of natural speech or live speech. But natural speech stimuli will have different spectra, fundamental frequencies, and temporal characteristics depending on the speaker, the source material and the language. For hearing aid verification measures to be comparable to each other it is necessary to have standardized stimuli that can be used internationally.

Alternative test stimuli have been proposed based on the long-term average speech spectrum (Byrne et al., 1994) or temporal envelope fluctuations (Fastl, 1987). The International Collegium for Rehabilitative Audiology (ICRA) developed a set of stimuli (Dreschler, 2001) that reflect the long-term average speech spectrum and have speech-like modulations that differ across frequency bands.  ICRA stimuli have advantages over modulated noise and sine wave stimuli in that they share some similar characteristics with speech, but they lack speech-like comodulation characteristics (e.g., fundamental frequency). Furthermore, ICRA stimuli are often classified by signal processing algorithms as “noise” rather than “speech”, so they are less than optimal for measuring how hearing aids process speech.

The European Hearing Instrument Manufacturers Association (EHIMA) is developing a new measurement procedure for nonlinear, adaptive hearing instruments and an important part of their initiative is development of a standardized test signal or International Speech Test Signal (ISTS).  The development and analysis of the ISTS was described in a paper by Holube, et al. (2010).

There were fifteen articulated requirements for the ISTS, based on available test signals and knowledge of natural speech, the most clinically salient of which are:

  • The ISTS should resemble normal speech but should be non-intelligible.
  • The ISTS should be based on six major languages, representing a wide range of phonological structures and fundamental frequency variations.
  • The ISTS should be based on female speech and should deviate from the international long-term average speech spectrum (ILTASS) for females by no more than 1dB.
  • The ISTS should have a bandwidth of 100 to 16,000Hz and an overall RMS level of 65dB.
  • The dynamic range should be speech-like and comparable to published values for speech (Cox et al., 1988; Byrne et al., 1994).
  • The ISTS should contain voiced and voiceless components. Voiced components should have a fundamental frequency characteristic of female speech.
  • The ISTS should have short-term spectral variations similar to speech (e.g., formant transitions).
  • The ISTS should have modulation characteristics similar to speech (Plomp, 1984).
  • The ISTS should contain short pauses similar to natural running speech.
  • The ISTS stimulus should have a 60 second duration, from which other durations can be derived.
  • The stimulus should allow for accurate and reproducible measurements regardless of signal duration.

Twenty-one female speakers of six different languages (American English, Arabic, Mandarin, French, German and Spanish) were recorded while reading a story, the text and translations of which came from the Handbook of the International Phonetic Association (IPA).  One recording from each language was selected based on a number of criteria including voice quality, naturalness and median fundamental frequency. The recordings were filtered to meet the ILTASS characteristics described by Byrne et al. (1994) and were then split into 500ms segments that roughly corresponded to individual syllables. These syllable-length segments were attached in pseudo-random order to generate sections of 10 or 15 milliseconds. Each of the resulting sections could be combined to generate different durations of the ISTS stimulus and no single language was used more than once in any 6-segment section.  Speech interval and pause durations were analyzed to ensure that ISTS characteristics would closely resemble natural speech patterns.

For analysis purposes, a 60-second ISTS stimulus was created by concatenation of 10- and 15-second sections.  This ISTS stimulus was measured and compared to natural speech and ICRA-5 stimuli based on several criteria:

  • Long-term average speech spectrum (LTASS)
  • Short term spectrum
  • Fundamental frequency
  • Proportion of voiceless segments
  • Band-specific modulation spectra
  • Comodulation characteristics
  • Pause and speech duration
  • Dynamic range (spectral power level distribution)

On all of the analysis criteria, the ISTS stimulus resembled natural speech stimuli as well or better than ICRA-5 stimuli. Notable improvements for the ISTS over the ICRA-5 stimulus were its comodulation characteristics and dynamic range of 20-30dB, as well as pauses and combinations of voiced and voiceless segments that more closely resembled the distributions in natural speech.  Overall, the ISTS was deemed an appropriate speech-like stimulus proposal for the new standard measurement protocol.

Following the detailed analysis, the ISTS stimulus was used to measure four different hearing instruments, which were programmed to fit a flat, sensorineural hearing loss of 60dBHL.  Each instrument was nonlinear with adaptive noise reduction, compression and feedback management characteristics. The first-fit algorithms from each manufacturer were used, with all microphones fixed to an omnidirectional mode.  Instead of yielding gain and output measurements across frequency for one input level, the results showed percentile dependent gain (99th, 65th and 30th) across frequency as referenced to the long-term average speech spectrum.  The percentile dependent gain values provided information about nonlinearity, in that the softer components of speech were represented by the 30th percentile, moderate and loud speech components were represented by the 65th and 99th percentiles, respectively.  Relations between these three percentiles represented the differences in gain for soft, moderate and loud sounds.

The measurement technique described by Holube and colleagues, using the ISTS stimulus, offers significant advantages over current measurement protocols with standard sine wave or noise stimuli. First and perhaps most importantly, it allows hearing instruments to be programmed to real-life settings with adaptive signal processing features active. It measures how hearing aids process a stimulus that very closely resembles natural speech, so clinical verification measures may provide more meaningful information about everyday performance. By showing changes in percentile gain values across frequency, it also allows compression effects to be directly visible and may be used to evaluate noise reduction algorithms as well. The authors also note that the acoustic resemblance of ISTS to speech with its lack of linguistic information may have additional applications for diagnostic testing, telecommunications or communication acoustics.

The ISTS is currently available in some probe microphone equipment and will likely be introduced in most commercially available equipment over the next few years. Its introduction brings a standardized speech stimulus, for the testing of hearing aids, to the clinic. An important component of clinical best practice is the measurement of a hearing aid’s response characteristics. This is most easily accomplished through insitu probe microphone measurement in combination with a speech test stimulus such as the ISTS.

References

American National Standards Institute (ANSI ). ANSI S3.22-2003. Specification of hearing aid characteristics. New York: Acoustical Society of America.

Byrne, D., Dillon, H., Tran, K., Arlinger, S. & Wibraham, K. (1994). An international comparison of long0term average speech spectra. Journal of the Acoustical Society of America, 96(4), 2108-2120.

Cox, R.M., Matesich, J.S. & Moore, J.N. (1988). Distribution of short-term rms levels in conversational speech. Journal of the Acoustical Society of America, 84(3), 1100-1104.

Dreschler, W.A., Verschuure, H., Ludvigsen, C. & Westerman, S. (2001). ICRA noises: Artificial noise signals with speech-like spectral and temporal properties for hearing aid assessment. Audiology, 40, 148-157.

Fastl, H. (1987). Ein Storgerausch fur die Sprachaudiometrie. Audiologische Akustik, 26, 2-13.

Holube, I., Fredelake, S., Vlaming, M. & Kollmeier, B. (2010). Development and analysis of an international speech test signal (ISTS). International Journal of Audiology, 49, 891-903.

International Electrotechnical Commission, 1994, IEC 60118-0. Hearing Aids: Measurement of electroacoustical characteristics, Bureau of the International Electrotechnical Commission, Geneva, Switzerland.

IPA, 1999. Handbook of the International Phonetic Association. Cambridge University Press.

Plomp, R. (1984). Perception of speech as a modulated signal. In M.P.R. van den Broeche, A. Cohen (eds), Proceedings of the 10th International Congress of Phonetic Sciences, Utrecht, Dordrecht: Foris Publications, 29-40.

 

 

 

Will placing a receiver in the canal increase occlusion?

The influence of receiver size on magnitude of acoustic and perceived measures of occlusion.

Vasil-Dilaj, K.A., & Cienkowski, K.M. (2010). The influence of receiver size on magnitude of acoustic and perceived measures of occlusion. American Journal of Audiology 20, 61-68.

This editorial discusses the clinical implications of an independent research study. The original work was not associated with Starkey Laboratories and does not reflect the opinions of the authors.

The occlusion effect, an increase in bone conducted sound when the ear canal is occluded, is a consideration for many hearing aid fittings.  The hearing aid shell or earmold restricts the release of low-frequencies from the ear canal (Revit, 1992), resulting in an increase in low-frequency sound pressure level at the eardrum, sometimes up to 25dB (Goldstein & Hayes, 1965; Mueller & Bright, 1996; Westermann, 1987).  Hearing aid users suffering from occlusion will complain of an “echo” or “hollow” quality to their voices and hearing their own chewing can be particularly annoying. Indeed, perceived occlusion is reported to be a common reason for dissatisfaction with hearing aids (Kochkin, 2000).

Occlusion from a hearing aid shell or earmold is usually managed by increasing vent diameter or decreasing the length of the vent in order to decrease the acoustic mass of the vent (Dillon, 2001; Kiessling, et al, 2005). One potential risk of increasing vent diameter is increased risk of feedback, but this problem has been alleviated by improvements in feedback cancellation. Better feedback management has also resulted in more widespread use of open fit, receiver-in-canal (RIC) instruments which have proven effective in reducing measured and perceived occlusion (Dillon, 2001; Kiessling et al., 2005; Kiessling et al., 2003; Vasil & Cienkowski, 2006).

Though open fit BTE hearing instruments are designed to be acoustically transparent, some open fittings still result in perceived occlusion.  Interestingly, perceived occlusion is not always strongly or even significantly correlated with measured acoustic occlusion (Kiessling et al., 2005; Kuk et al., 2005; Kampe & Wynne, 1996), so it is apparent that other factors do contribute to the perception of occlusion.  The size of the receiver and/or eartip, as well as the size of the ear canal, affect the amount of air flow in and out of the ear canal and it seems likely that these factors could affect the amount of acoustic and perceived occlusion.

Thirty adults, 17 men and 13 women, participated in the study. All had normal hearing, unremarkable otoscopic examinations and normal tympanograms. Two measures of ear canal volume were obtained: volume estimates from the tympanometry screener and estimates determined from earmold impressions that were sent to a local hearing aid manufacturer.  Participants were fitted binaurally with RIC hearing instruments.  Instead of domes used clinically with RIC instruments flexible receiver sleeves designed specifically for research purposes were used.  Use of the special receiver sleeves allowed the researchers to increase the overall circumference of the receiver systematically so that six receiver size conditions could be evaluated:  no receiver, receiver only (with a circumference of 0.149 in.), 0.170 in., 0.190 in., 0.210in. and 0.230 in.

Real-ear unoccluded and occluded measures were obtained with subjects vocalizing the vowel /i/. Subjects monitored the level of their vocalizations via a sound level meter. Real ear occlusion effect (REOE) was determined by subtracting the SPL levels for the unoccluded response from the occluded response (REOR-REUR = REOE).  Subjective measures were obtained by asking subjects to rate their perception of occlusion on a five point scale ranging from “no occlusion” to “complete occlusion”. To avoid bias in the occlusion ratings, participants were not allowed to view the hearing aids or receiver sleeves until after testing was completed.

Results indicated that measured acoustic occlusion was very low for all conditions, especially below 500Hz, where it was below 2dB for most of the receiver conditions. For frequencies above 500Hz, REOE increased as receiver size increased. The no receiver and receiver only conditions had the least amount of measured occlusion and the largest receiver sizes had the most. There was no significant interaction between receiver size and frequency.

Perceived occlusion also increased as receiver size increased and though it was mild for most participants in most of the conditions, for the largest receiver condition, some participants rated occlusion as severe. Perceived occlusion was not significantly correlated with measured acoustic occlusion for low frequencies, and the two measures were only weakly correlated for frequencies between 700-1500Hz.

There was no significant relationship between either measure of ear canal volume and perceived or acoustic measures of occlusion. However, adequate ear canal volume to accommodate all receiver sizes was an inclusion criterion for the study, so the authors suggest that smaller ear canal volume could still be a factor in perceived or acoustic occlusion and may warrant further study.

The results of the current investigation show that occlusion was minimal for most of the receiver sizes. These findings are in agreement with previous studies of vented hollow molds, completely open IROS shells (Vasil & Cienkowski, 2006), large 2.4mm vents and silicone ear tips (Kiessling et al, 2005). REOEs for the two largest receivers matched results for a hollow mold with 1mm vent (Kuk et al, 2009) and the REOEs for the two smallest receivers matched results for hollow molds with 2mm and 3mm vents (Kuk et al, 2009).  The authors also point out that there was minimal insertion loss for all conditions. Insertion loss from closed earmolds can amount to 20dBHL (Sweetow, 1991) and can contribute to a perception of occlusion or poor voice quality.  The relative lack of insertion loss is yet another potential advantage of open and RIC fittings.

Perception of occlusion did increase with the size of the receiver, but overall differences were small. This is in agreement with prior research suggesting that reduction of air flow out of the ear canal results in more low-frequency energy in the ear canal (Revit, 1992), which can cause an increase in occlusion (Dillon, 2001). The authors point out that although subjects were not able to see the receivers prior to insertion, they were probably aware of the size and weight differences and could have been influenced by the perception of a larger object in the ear as opposed to actual occlusion. This may also be the case for hearing aid users, perhaps particularly so for individuals with smaller or tortuous ear canals.

The occlusion effect can be challenging, especially when anatomical or other constraints result in the use of minimal venting for individuals with good low-frequency hearing. The results reported here suggest that acoustic occlusion with RIC instruments is slight and may not always be related to perceived occlusion. Therefore, a client’s perception of “hollow” voice quality, “echoey” sound quality or a plugged sensation may be the most reliable indication of occlusion and the most important determinant of eartip size or venting characteristics. The administration of an occlusion rating scale or other self-evaluation techniques may also prove helpful in evaluating occlusion and its impact on overall hearing aid satisfaction.

References

Dillon, H. (2001). Hearing aids. New York, NY: Thieme.

Goldstein, D.P.,  & Hayes, C.S. (1965). The occlusion effect in bone conduction hearing.  Journal of Speech and Hearing Research 8, 137-148.

Kampe, S.D., & Wynne, M.K. ( 1996). The influence of venting on the occlusion effect. The Hearing Journal 49(4), 59-66.

Kiessling, J., Brenner, B., Jespersen, C.T., Groth, J., & Jensen, O.D. (2005). Occlusion effect of earmolds with different venting systems. Journal of the American Academy of Audiology, 16, 237-249.

Kiessling. J., Margolf-Hackl, S., Geller, S., & Olsen, S.O. (2003). Researchers report on a field test of a non-occluding hearing instrument. The Hearing Journal , 56(9), 36-41.

Kochkin, S. (2000). MarkeTrak V: Why my hearing aids are in the drawer: The consumer’s perspective. The Hearing Journal 53 (2), 34-42.

Kuk, F.K. , Keenan, D., & Lau, C.C. (2005). Vent configurations on subjective and objective occlusion effect. Journal of the American Academy of Audiology 16, 747-762.

Mueller, H.G., & Bright, K.E. (1996). The occlusion effect during probe microphone measurements. Seminars in Hearing 17 (1), 21-32.

Revit, L. (1992). Two techniques for dealing with the occlusion effect. Hearing Instruments 43 (12), 16-18.

Sweetow, R. W. (1991). The truth behind “non-occluding” earmolds. Hearing Instruments 42 (1), 25.

Vasil, K.A., & Cienkowski, K.M. (2006). Subjective and objective measures of the occlusion effect for open-fit hearing aids. Journal of the Academy of Rehabilitative Audiology 39, 69-82.

Vasil-Dilaj, K.A., & Cienkowski, K.M. (2010). The influence of receiver size on magnitude of acoustic and perceived measures of occlusion. American Journal of Audiology 20, 61-68.

Westermann, V.H. (1987). The occlusion effect. Hearing Instruments, 38 (6), 43.

Understanding the best listening configurations for telephone use when wearing hearing aids

Understanding the best listening configurations for telephone use when wearing hearing aids

Picou, E.M. & Ricketts, T.A. (2010) Comparison of wireless and acoustic hearing aid based telephone listening strategies. Ear and Hearing 31(6), 1-12.

This editorial discusses the clinical implications of an independent research study. The original work was not associated with Starkey Laboratories and does not reflect the opinions of the authors.

Telephone use is an important consideration for hearing aid users. It is often challenging to arrive at the appropriate coupling method to the ear and related hearing aid settings. Many people with hearing loss have difficulty hearing on the telephone and concerns about telephone use may result in reluctance to purchase new hearing aids or to use aids that have already been purchased (Kochkin, 2000).  Indeed, in a survey of hearing aid satisfaction, one in five respondents reported dissatisfaction when using the telephone with a hearing aid (Kochkin, 2005).

There are a number of factors that affect a hearing aid user’s ability to hear on the phone, including lack of visual cues, reduced bandwidth, background noise and difficulty coupling the phone to the hearing aid. The lack of visual cues has been addressed recently with videoconferencing applications, but these are not commonly used, especially among older individuals. The reduced bandwidth (approximately 300 to 3,300 Hz) is characteristic of sound transmission over the phone, so there is little an individual can do improve the availability of high frequency speech cues over the phone. Background noise and coupling issues can be addressed in a number of ways, depending on the individual and the circumstances.

There are two ways a hearing aid can be coupled directly to the telephone; acoustically and with an inductive telecoil  or with acoustic settings that focus on the telephone’s limited frequency range. A drawback to the acoustic setting is that the hearing aid microphone is active which may result in feedback (Latzel et. al., 2001; Palmer, 2001; Chung, 2004).  Despite recent improvements in feedback control, this remains a problem, especially for those with severe hearing loss whose hearing aids require more gain.  Additionally, the microphone picks up environmental noise that competes with the telephone signal, decreasing the signal to noise ratio.  Telecoils can be a solution for feedback and poor signal to noise ratios, but they are subject to interference from fluorescent lights, computer equipment and power lines.  Furthermore, it can be difficult to determine the proper positioning of the phone for optimal sound quality, as the telephone receiver must be placed as close to the telecoil as possible (Tannahill, 1983; Compton, 1994; Yanz & Preves, 2003).

A recent option for telephone is through the use of intermediate wireless accessories, these route sound from the phone to the hearing aids via a combination of Bluetooth and a direct-to-hearing aid wireless technology. These devices address the problems with acoustic or telecoil coupling, and have the possibility of providing some additional benefit if the telephone signal is bilaterally routed (Green, 1976; Moore, 1998; Hall et al, 1984; Quaranta and Cervellera, 1974).  Many hearing aid manufacturers offer wireless devices, but it is unclear whether their use results in significantly improved speech recognition over the phone. Even with wireless routing of the phone signal, there may still be detrimental effects of background noise, especially for individuals with open-canal hearing aids (Dillon, 1985; 1991).

The purpose of Picou and Ricketts’ study was to examine speech recognition performance with monaural and binaural wireless phone transmission, as well as a monaural acoustic condition, in the presence of two levels of background noise. They also evaluated performance with occluding versus non-occluding domes.

Twenty individuals with sloping, high-frequency, sensorineural hearing loss participated in the study. Subjects were fitted with binaural, receiver-in-canal hearing instruments with a wireless transmitter accessory. Half of the subjects were tested with open, non-occluding domes and half were tested with closed, occluding domes.

A total of seven hearing aid and telephone configurations were tested in two background noise levels (55dBA and 65dBA). Subjects responded to sentences from the Connected Speech Test (CST, Cox et al., 1987).  Speech stimuli were band pass filtered from 300 to 3400Hz to simulate telephone transmission and presented at 65dB.  Competing speech babble was presented through four loudspeakers positioned around the listener at a distance of 1 meter. All test conditions – hearing aid condition, dome type, noise level – were counterbalanced to avoid effects of learning and fatigue.

This study illuminates some important considerations in telephone use and supports the use of wireless telephone accessories, especially with bilateral routing.  The participants subjects performed best with external hearing aid microphones turned off, but the authors acknowledge that for safety and monitoring of environmental sounds, it may be advisable to leave microphones active at an attenuated level. The authors suggest that further investigation is warranted to determine optimal levels of microphone attenuation to allow for successful speech recognition over the phone, while preserving environmental awareness.

Performance with occluding domes was better than open domes for wireless telephone signal routing in noise. Occluding domes reduce the environmental noise entering the ear canal, providing an improvement in signal to noise ratio. In the acoustic phone condition, open domes performed better than occluding domes. Subjects tended to position the phone directly over the ear canal which likely improved signal to noise ratio by blocking background noise and isolating the speech transmitted from the phone.

Specific observations were made for participants wearing open-canal hearing aids. Specifically, users with open domes should be instructed to hold the phone directly over the ear canal for optimal speech recognition. Programming adjustments may be necessary to increase availability of low and mid-frequency speech cues and improve signal to noise ratio.  Conversely, users with occluding domes should be advised of the potential limitations of direct acoustic coupling to the phone and should be instructed to hold the phone receiver as close to the microphone as possible. Alternatively, patients with occluding domes may be better off using a telecoil, if available, for situations in which they cannot use a wireless device.

Interestingly, the no significant improvement in speech recognition resulted from plugging the non-test ear or muting the hearing aid on the non-test ear.  This is consistent with previous research on masking level differences for tones (Green, 1976; Moore 1998) as well as a previous study of speech recognition over the phone, which found no improvement for normal-hearing listeners when the non-phone ear was plugged.  This is inconsistent, however, with reported preferences of hearing aid users.  Despite the lack of improvement in the current study, the authors acknowledged that muting the hearing aid on the non-phone ear may reduce listening effort, which is therefore preferred by the listener.

For users of wireless accessories, the results of this study clearly indicate that binaural routing is ideal. But for hearing aid users who do not have wireless devices, the optimal hearing aid settings and coupling method may depend on several factors. The extent of venting or openness should be considered when choosing an acoustic phone coupling; individuals with minimal venting may not hear well unless they are able to hold the telephone over the hearing aid microphone, while patients with open fittings may experience more challenges with background noise interference than the more occluded wearer.

Regardless of whether a client uses an intermediate wireless device for binaural telephone streaming, monaural acoustic listening or telecoil coupling, the attenuation level of the hearing aid microphones is also a consideration. For binaural wireless routing or streaming it is advisable to keep both hearing aid microphones active but attenuated, to preserve awareness of environmental sounds. For monaural acoustic/telecoil combinations the microphone level on the opposite ear can be attenuated slightly to allow environmental awareness but reduce distraction from surrounding noise. As noted earlier, further study is warranted to determine optimal microphone attenuation levels.

References

Chung, K. (2004). Challenges and recent developments in hearing aids. Part II. Feedback and occlusion effect reduction strategies, laser shell manufacturing processes and other signal processing technologies. Trends in Amplification 8, 125-164.

Compton, C. (1994). Providing effective telecoil performance with in-the-ear hearing instruments. Hearing Journal 47, 23-26.

Cox, R.M., Alexander, G.C. & Gilmore, C.A. (1987). Development of the connected speech test (CST). Ear and Hearing, 8 (supplement): 119S-126S.

Dillon, H. (1985). Earmolds and high frequency response modification. Hearing Instruments 36, 8-12.

Dillon, H. (1991). Allowing for real ear venting effects when selecting the coupler gain of hearing aids. Ear and Hearing 12(6), 406-416.

Green, D.M. (1976). An Introduction to Hearing. Hillsdale, NJ: Lawrence Erlbaum Associates.

Hall, J.W., Tyler, R.S., Fernandes, M.A. (1984). Factors influencing the masking level difference in cochlear hearing-impaired and normal-hearing listeners. Journal of Speech and Hearing Research 27, 145-154.

Hawkins, D.B. (1984). Comparisons of speech recognition in noise by mildly-to-moderately hearing-impaired children using hearing aids and FM systems. Journal of Speech and Hearing Disorders 49, 409-418.

Kochkin, S. (2000). MarkeTrak V: “Why my hearing aids are in the drawer”: The consumers’ perspective. Hearing Journal 53, 34-42.

Kochkin, S. (2005). MarkeTrak VII: Customer satisfaction with hearing aids in the digital age. Hearing Journal 58, 30-39.

Latzel, M., Gebhart, T.M. & Kiessling, J. (2001). Benefit of a digital feedback suppression system for acoustical telephone communication. Scandanavian Audiology Supplementum 52, 69-72.

Moore, B.C.J. (1998). Cochlear Hearing Loss. London: Whurr Publishers.

Palmer, C.V. (2001). Ring, ring! Is anybody there? Telephone solutions for hearing aid users. Hearing Journal 54, 10.

Picou, E.M. & Ricketts, T.A. (2010) Comparison of wireless and acoustic hearing aid based telephone listening strategies. Ear and Hearing 31(6), 1-12.

Quaranta, A. & Cervellera, G. (1974). Masking level difference in normal and pathological ears. Audiology 13, 428-431.

Tannahill, J.C. (1983). Performance characteristics for hearing aid microphone versus telephone and telephone/telecoil reception modes. Journal of Speech and Hearing Research 26, 195-201.

Yanz, J.L. & Preves, D. (2003). Telecoils: Principles, pitfalls, fixes and the future. Seminars in Hearing 24, 29-41.

 

 

The DSL 5.0a is a successful fitting formula for adults

Fit to Targets, Preferred Listening Levels, and Self-Reported Outcomes for the DSL v5.0a Hearing Aid Prescription for Adults

Polonenko, M.J., Scollie, S.D., Moodie, S., Seewald, R.C., Laurnagaray, D., Shantz, J. & Richards, A. (2010) Fit to targets, preferred listening levels and self-reported outcomes for the DSL v5.0a hearing aid prescription for adults. International Journal of Audiology 49, 550-560.

This editorial discusses the clinical implications of an independent research study. The original work was not associated with Starkey Laboratories and does not reflect the opinions of the authors.

The importance of perceived benefit for successful hearing aid fittings is well established. According to two MarkeTrak studies by Sergei Kochkin (2005, 2007), perceived benefit was the number one factor contributing to hearing aid user satisfaction.  Similarly, the lack of benefit was the most commonly cited reason for hearing aid returns.  Perceived benefit from hearing aids may be determined by a number of factors, but the appropriateness of the individually fitted gain is one of the main contributors (Cox & Alexander, 1994).

The Desired Sensation Level (DSL) prescriptive method was originally developed for children and prescribes targets that are generally very close to children’s preferred listening levels. However, DSL v4.1 targets have been found to prescribe gain that is 9 to 11 dB greater than adult preferred listening levels (Scollie et al., 2005).  Therefore, DSL v5.0a was developed with lower perceived loudness levels, ones that more closely approximate the needs of adult hearing aid users.

The success of a hearing aid prescription can be measured in terms of clinical efficacy, or how closely the hearing aid settings achieve a desired clinical result or test outcome. One such measure is the Preferred Listening Level (PLL). The PLL is defined as “the sound pressure level at the eardrum that the person chooses or prefers for listening to hearing aid amplified speech”(Cox & Alexander, 1994) and represents a compromise between comfort, intelligibility, background noise and distortion (Cox, 1982).  One method of measuring the PPL is by instructing listeners to adjust the volume setting of their hearing instruments to the level that sounds best to them, as they listen to speech presented at a conversational level.

A related but different way to determine the success of a hearing aid fitting strategy is measure effectiveness, or how well hearing aid settings help the user function in real-world situations.  One commonly used measure of hearing aid effectiveness is the Client Oriented Scale of Improvement or COSI (Dillon et al., 1997).  On the COSI questionnaire, the hearing aid user lists up to 5 typical listening situations in which he struggles to hear or would like to hear better.  Following a period of acclimatization, they rate the degree of perceived change in these situations as well as their final ability to function in each situation.

Although the DSL v5.0a prescriptive method was specifically developed for adults with acquired hearing loss, there have been relatively few studies evaluating it. Therefore the current authors sought to determine the electroacoustic feasibility, clinical efficacy, and effectiveness with adult hearing aid users. They had three primary goals:

1.  To measure final fit versus targets in a clinical environment

2.  To evaluate the preferred listening levels (PLLs) of adults versus the DSL v5.0a targets

3.  To measure the effectiveness of the DSL v5.0a prescription as reported on the COSI

Thirty subjects with predominantly sensorineural hearing loss participated in the study. Nineteen were new hearing aid users and eleven were experienced hearing aid users. Twenty-four were fitted binaurally, six were monaural users. Subjects were fitted in private clinics and the audiologists were specifically instructed to program and adjust the instruments to meet the patients’ needs, rather than to meet prescriptive targets.

Hearing aid fittings were matched to DSL 5.0 prescribed targets and verified with simulated real ear measurements, to ensure consistency between test sites and to promote replicable measures. Hearing aids were set to their primary programs and were measured in 2cc couplers, after individual Real Ear to Coupler Differences (RECD) were measured.  Following electroacoustic measures, the aids were fitted to the patients’ ears and adjustments were made based on patients’ subjective satisfaction. These procedures were not carried out according to any protocol established by the authors; the audiologists conducted fine tuning adjustments as needed for each individual. After an approximately 30-day period, subjects returned to the clinics for fine tuning.  After a total acclimatization period of 90 days, preferred listening levels (PLLs) and COSI outcome evaluations were conducted.

Electroacoustic analyses revealed that the clinical fittings were significantly correlated with the DSL v5.0a targets.  Sixty-eight percent of initial fittings were within 2.9 to 4.2 dB of target and 95% were within 5.8 to 8.4 dB of target across frequencies. These results contrast with previous research using NAL-R and NAL-NL1 targets, in which initial fittings differed from targets by 10-15dB. (Sammeth, 1993; Aazh and Moore, 2007).

Preferred listening levels (PLLs) were compared to targets and initial fittings and differed by only about 2dB.  The DSL v5.0a targets were on average 2.6dB lower than PLLs and 1.95dB lower than initial fittings.  Furthermore, DSL v5.0a targets were significantly correlated with PLLs at all frequencies and the targets and PLLs did not differ significantly as a function of degree of hearing loss.  The authors noted a trend for higher PLLs than targets at 250Hz, indicating that some users preferred more low-frequency output than prescribed.

COSI ratings of real-world performance were obtained at the 90-day appointment. The top five situations in which subjects hoped to hear better were similar to those chosen by subjects in the COSI normative study (Dillon et al, 1999):

1.  conversation with a group in noise

2.  conversation with a group in quiet

3.  conversation with one or two partners in noise

4.  listening to the television or radio

5.  conversation with one or two partners in quiet

Subjects were asked to rate the degree of change in their hearing with amplification as well as the final hearing ability (or hearing aid performance) in these situations. Results indicated that they judged their hearing to be “better” or “much better” for 83% of the fittings, which compares well to the normative results obtained by Dillon et al. (1999) of 80%. For final hearing ability, 93% of the current respondents reported hearing 75% of the time (a COSI rating of 4 or better) as compared to 90% of the normative study participants.

The purpose of the current study was to determine if DSLv5.0a prescriptive targets, developed for adults, provided electroacoustically appropriate fittings and subjectively favorable real-world results.  Indeed, clinician-adjusted fittings were within 10 dB of prescriptive targets for 92% of the subjects.  Targets also closely approximated preferred listening levels, which is particularly important because prior studies showed DSL v4.1 targets were generally higher than adults’ preferred levels.  COSI measurements indicated positive ratings for benefit and communication performance which were similar or slightly better than those obtained for the normative population.

An incidental finding of the current study was that instruments with more than six channels of processing may meet prescriptive targets more accurately than those with only six channels.  This was not specifically studied in the current paper, but the authors provided a matrix of number of channels versus errors in matching to target, showing that instruments with more than six channels yielded fewer and smaller errors than those with only six channels of processing. This result is probably consistent with clinical observations, in which sophisticated hearing aid circuits with more channels of processing often provide better fittings than instruments with fewer channels.  The importance of this factor may depend on the client’s hearing loss.  Gently sloping audiometric configurations may generally require fewer channels to meet targets.

The current results show that in a group of adults preferred listening levels and positive real-world outcomes were achieved with programs matched to DSL v5.0a targets, at least in quiet situations. In noisy listening situations, participants may have accessed alternate memories with directionality and noise reduction, causing amplification characteristics to differ from DSL settings.  Even if this is the case, the current study shows that the DSL v5.0a prescriptive measure for adults yields a close approximation to patient preferred settings for a wide range of hearing losses.

References

Aazh, H. &Moore, B.C.J. (2007). The value of routine real ear measurement of the gain of digital hearing aids. Journal of the American Academy of Audiology 18, 653-664.

Cox, R.M. (1982). Functional correlates of electroacoustic performance data. In: G.A. Studebaker & F.H. Bess (eds.) The Vanderbilt Hearing Aid Report. Parkton, MD: York Press, pp. 78-84.

Cox, R.M. & Alexander, G.C. (1994). Prediction of hearing aid benefit: the role of preferred listening levels. Ear and Hearing 15(1), 22-29.

Dillon, H., James, A. & Ginis, J. (1997). Client Oriented Scale of Improvement (COSI) and its relationship to several other measures of benefit and satisfaction provided by hearing aids. Journal of the American Academy of Audiology 8, 27-43.

Dillon, H., Birtles, G. & Lovegrove, R. (1999). Measuring the outcomes of a National Rehabilitation Program: normative data for the Client Oriented Scale of Improvement (COSI) and the Hearing Aid User’s Questionnaire (HAUQ). Journal of the American Academy of Audiology 10, 67-79.

Kochkin, S. (2005). MarkeTrak VII: Customer satisfaction with hearing instruments in the digital age. Hearing Journal 58(9), 30-43.

Kochkin, S. (2008). MarkeTrak VII:  Obstacles to adult non-user adoption of hearing aids. Hearing Journal 60(4), 24-51.

Polonenko, M.J., Scollie, S.D., Moodie, S., Seewald, R.C., Laurnagaray, D., Shantz, J. & Richards, A. (2010) Fit to targets, preferred listening levels and self-reported outcomes for the DSL v5.0a hearing aid prescription for adults. International Journal of Audiology 49, 550-560.

Sammeth, C., Peek, B., Bratt, G., Bess, F. & Amberg, S. (1993). Ability to achieve gain/frequency response and SSPL-90 under three prescription formulas with in-the-ear hearing aids. Journal of the American Academy of Audiology 4, 33-41.

Scollie, S., Seewald, R., Cornelisse, L., Moodie, S., Bagatto, M., et al. (2005). The Desired Sensation Level Multistage Input/Output Algorithm. Trends in Amplification 4(9), 159-197.

Understanding the benefits of bilateral hearing aids

A Prospective Multi-Centre Study of the Benefits of Bilateral Hearing Aids

Boymans, M., Goverts, S.T., Kramer, S.E., Festen, J.M. & Dreschler, W.A. (2008). A prospective multi-centre study of the benefits of bilateral hearing aids. Ear and Hearing 29(6), 930-941.

This editorial discusses the clinical implications of an independent research study. The original work was not associated with Starkey Laboratories and does not reflect the opinions of the authors.

The benefits of binaural amplification are generally well established and include improved speech discrimination in noise (Hawkins and Yacullo, 1984; Kobler & Rosenhall, 2002), improved localization of sound sources (Dreschler & Boymans, 1994; Punch et al, 1991) perception of balanced hearing, improved speech clarity (Chung & Stephens, 1986; Erdman & Sedge, 1981) and reduced listening  effort (Noble, 2006). However, some studies have shown either little subjective difference between unilateral and bilateral amplification (Andersson et al, 1996) or even a subjective preference for unilateral hearing aids, especially in noise (Walden & Walden, 2005; Schreurs & Olsen, 1985).

The authors of the current study sought to confirm subjective evaluations of binaural hearing aids with objective, functional tests of localization and speech discrimination in noise. They also examined three diagnostic measures to determine their potential as predictors of binaural success.

Two hundred fourteen hearing-impaired subjects were recruited from eight audiology clinics in the Netherlands. Participant inclusion criteria were limited only to  participants who were native Dutch speakers and were physically able to complete the test procedures, with no contraindications for binaural hearing aid fitting. Therefore, individual characteristics varied widely with regard to prior hearing aid use, hearing aid style and circuitry, age and degree of hearing loss. Ten participants with normal hearing were also tested for reference purposes.

Prior to hearing aid fitting, in addition to basic diagnostic audiometry, participants completed three tests that were chosen as potential predictors of binaural benefit:

1. Interaural time differences.

2. Binaural masking level differences.

3. Speech reception thresholds in background noise.

Following the hearing aid fittings, functional binaural benefit was evaluated and questionnaires were administered to obtain subjective responses to unilateral and bilateral fittings. Three assessment tools were used:

1. Speech intelligibility in background noise with spatial separation of speech and noise.

2. Horizontal localization of everyday sounds.

3. Subjective questionnaires to examine differences between unaided, unilateral, and bilateral conditions for detection of sounds, discrimination of sounds, speech intelligibility in quiet and noise, localization, and comfort of loud sounds.

Not surprisingly, on all three diagnostic measures, normal hearing participants performed significantly better than hearing-impaired participants. There was a great deal of inter-participant variability within the hearing-impaired group.

On the functional test of speech intelligibility with spatially separated speech and noise, bilateral hearing aid users performed significantly better than unilateral hearing aid users. Improvements were noted for conditions in which competing sounds were presented ipsilateral and contralateral to the speech stimulus.  On the localization test, bilateral hearing instrument wearers again performed significantly better than unilateral hearing aid wearers.  Subjective questionnaires showed that unilateral hearing aid use was favored over unaided conditions for all categories except comfort of loud sounds. Similarly, bilateral hearing aid use was favored over unilateral for all categories except comfort of loud sounds.  This finding is in agreement with previous work by the lead author of the current study (Boymans, 2003).

Participants were asked to provide reasons why they preferred one or two hearing aids. The most common reason for preferring a unilateral fitting was that the user’s own voice was more pleasant with one hearing aid. For preferred bilateral fittings, the most common reasons were, intelligibility on both sides, better localization, better sound quality, and better balance.  Following completion of the study, 93% of the participants chose to purchase bilateral hearing aids, whereas 7% chose to purchase only one hearing aid.

One primary goal of the study was to determine if subjective benefit could be supported with objective test results. There was a significant positive correlation between bilateral benefit for speech perception and subjective satisfaction ratings, but other evaluated factors did not show this relationship. Therefore, the authors determined that functional test results could not distinguish between groups who preferred unilateral or bilateral fittings. Overall, however, the vast majority of participants preferred bilateral hearing aid fittings and the functional test results support a strong binaural benefit.

The second goal of the study was to evaluate potential predictive measures of binaural benefit. The results did not show strong correlations between bilateral hearing aid performance and interaural time difference, binaural masking level difference or speech reception threshold measures.  Therefore, these measures were not determined to have particular predictive value for determining binaural hearing aid success.  In fact, the strongest correlation between bilateral benefit and any other diagnostic measure was found for traditional audiometric measures of pure tone average and maximum speech recognition.

Binaural benefit was also examined with regard to other subject variables. The authors found greater binaural benefit for users with more severe hearing loss and for those with more symmetrical hearing loss. There were no significant differences between subjects who had previously been fitted with unilateral hearing aids and those who had been previously fitted bilaterally. Participants without prior hearing aid experience demonstrated slightly less binaural benefit and less satisfaction than those with previous experience. The authors point out that this finding is confounded by the fact that previous users tended to have significantly greater degrees of hearing loss than first-time users.

The bilateral benefit for localization was higher for in-the-ear hearing aid users than for behind-the-ear hearing aid users. The authors surmised that this could be related to pinna effects, but pinna effects generally aid vertical localization and front/back localization (Blauert, 1997), whereas the localization measures in the current study were strictly horizontal. Still, it is possible that preservation of pinna-related spectral cues in combination with binaural cues could have had an additive effect for the in-the-ear hearing aid users in the present study.

It is interesting to note that despite the highly variable subject population in this study, significant binaural benefit for speech intelligibility and localization was found across participants, and participants overwhelmingly preferred the use of binaural hearing aids over monaural. Variables such as microphone mode, noise reduction technology, and circuit quality were not specifically addressed or controlled. It is reasonable to surmise that performance in the one category in which subjects preferred unilateral hearing aids, comfort for loud sounds, could be improved by adjustments to noise reduction settings, MPO or gain settings, or use of adaptive directionality.  Therefore, the study as a whole offers strong support for binaural hearing aid recommendations and indicates that the only negative effect, that of loudness discomfort, could probably be easily corrected with current technology.

Participants in this study were all willing to consider binaural hearing aid use and therefore had relatively symmetrical hearing losses. The binaural benefits measured here can probably be reasonably extrapolated to individuals with asymmetrical hearing losses, but this issue might benefit from further study.  Also, it is likely that similar binaural benefits may also apply to potential hearing aid users who are unwilling or reluctant to consider binaural hearing aid use, but these clients will require more thorough counseling with regard to expectations and acclimatization.  The primary reason given for unilateral hearing aid preference was related to occlusion and the sound quality of one’s own voice. A reluctant user of new binaural hearing aids will need to understand that this is a common, but often short-lived, outcome of binaural hearing aid use.

Because of the poor predictive value of diagnostic tests for binaural hearing aid success, the authors advise that it is probably best for hearing aid users to determine binaural benefit individually, during their initial trial period. This is appropriate advice and may be in line with what most clinicians are already recommending to their patients. Because an individual’s work, home, and social activities are important determinants of their perceived hearing handicap, binaural hearing aids should always be tested thoroughly in these situations to evaluate benefit.  There is little financial risk involved, as most clinics offer at least a 30-day trial period with new instruments and many offer a 45- or 60-day trial. Should a client determine that the benefit of a second hearing aid does not outweigh the financial burden, they would be able to return the aid for a refund, losing only the cost of a custom earmold and/or a trial period fee.

The current study shows strong evidence for functional improvements as well as perceived advantages in binaural hearing aid users. However, the authors were unable to identify a diagnostic tool to effectively predict binaural success.  This raises an important question about the value of such a predictive measure.  The significant improvements enjoyed by binaural users and the overwhelming preference for two hearing aids over one suggest that binaural fittings should be the recommendation of choice for all clients with bilateral, aidable hearing loss.  Granted, there are some audiometric findings that preclude a binaural recommendation, such as profound hearing loss in one ear, normal hearing in one ear, or exceptionally poor word recognition ability in one ear. But these are obvious, well-known, and relatively uncommon clinical contraindications to binaural hearing aid use. It seems reasonable, as the authors eventually suggest, to forego predictive measures and allow clients to experience binaural benefits individually and determine the proper decision for themselves during their trial period.

References

Andersson, G., Palmkvist, A., Melin, L. (1996). Predictors of daily assessed hearing aid use and hearing capability using visual analogue scales. British Journal of Audiology 30, 27-35.

Blauert, J. (1997). Spatial Hearing: The Psychophysics of Human Sound Localization. Cambridge: MIT Press.

Boymans, M. (2003). Intelligent processing to optimize the benefits of hearing aids. Ph.D. thesis, University of Amsterdam.

Boymans, M., Goverts, S.T., Kramer, S.E., Festen, J.M. & Dreschler, W.A. (2008). A prospective multi-centre study of the benefits of bilateral hearing aids. Ear and Hearing 29(6), 930-941.

Chung, S.M. & Stephens, S.D. (1986).  Factors influencing binaural hearing aid use. British Journal of Audiology 20, 129-140.

Dreschler, W.A. & Boymans, M. (1994). Clinical evaluation on the advantage of binaural hearing aid fittings. Audiologische Akustik 5, 12-23.

Erdman, S.A.  & Sedge, R.K. (1981). Subjective comparisons of binaural versus monaural amplification. Ear and Hearing 2, 225-229.

Hawkins, D.B. & Yacullo, W.S. (1984). Signal-to-noise ratio advantage of binaural hearing aids and directional microphones under different levels of reverberation. Journal of Speech and Hearing Disorders 49, 278-186.

Kobler, S. & Rosenhall, U. (2002). Horizontal localization and speech intelligibility with bilateral and unilateral hearing aid amplification. International Journal of Audiology 41, 395-400.

Noble, W. (2006). Bilateral hearing aids: a review of self-reports of benefit in comparison with unilateral fitting. International Journal of Audiology 45, 63-71.

Punch, J.L., Jenison, R.L. & Alan, J. (1991). Evaluation of three strategies for fitting hearing aids binaurally. Ear and Hearing 12, 205-215.

Schreurs, K.K. & Olsen, W.O. (1985). Comparison of monaural and binaural hearing aid use on a trial period basis. Ear and Hearing 6, 198-202.

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

A comparison of Receiver-In-Canal (RIC) and Receiver-In-The-Aid (RITA) hearing aids

Article of interest:

The Effects of Receiver Placement on Probe Microphone, Performance and Subjective Measures with Open Canal Hearing Instruments

Alworth, L., Plyler, P., Bertges-Reber, M. & Johnstone, P. (2010)

This editorial discusses the clinical implications of an independent research study. The original work was not associated with Starkey Laboratories and does not reflect the opinions of the authors.

Open-fit behind-the-ear hearing instruments are favored by audiologists and patients alike, because of their small size and discreet appearance, as well as their ability to minimize occlusion. The performance of open-fit instruments with the Receiver-In-The-Aid (RITA) and Receiver-In-Canal (RIC) has been compared to unaided conditions and to traditional, custom-molded instruments. However, few studies have examined the effect of receiver location on performance by comparing RITA and RIC instruments to each other. In the current paper, Alworth and her associates were interested in the effect of receiver location on:

– occlusion

– maximum gain before feedback

– speech perception in quiet and noise

– subjective performance and listener preferences

Theoretically, RIC instruments should outperform RITA instruments for a number of reasons. Delivery of sound through the thin tube on a RITA instrument can cause peaks in the frequency response, resulting in upward spread of masking (Hoen & Fabry, 2007). Such masking effects are of particular concern for typical open-fit hearing aid users; individuals with high-frequency hearing loss. RIC instruments are also capable of a broader bandwidth than RITA aids (Kuk & Baekgaard, 2008) and may present lowered feedback risk because of the distance between the microphone and receiver (Ross & Cirmo, 1980), and increased maximum gain before feedback (Hoen & Fabry, 2007; Hallenbeck & Groth, 2008).

The authors recruited twenty-five subjects with mild to moderate, high frequency, sensorineural hearing loss participated in the study. Fifteen had no prior experience with open-canal hearing instruments, whereas 10 had some prior experience. Each subject was fitted bilaterally with RIC and RITA instruments with identical signal processing characteristics, programmed to match NAL-NAL1 targets. Directional microphones and digital noise reduction features were deactivated. Subjects used one instrument type (RIC or RITA) for six weeks before testing and then wore the other type for six weeks before being tested again. The instrument style was counterbalanced among the subjects.

Probe microphone measures were conducted to evaluate occlusion and maximum gain before feedback. Speech perception was evaluated with the Connected Speech Test -CST (Cox et al, 1987), the Hearing in Noise test -HINT (Nilsson, et al, 1994), the High Frequency Word List – HFWL (Pascoe, 1975) and the Acceptable Noise Level – ANL test (Nabelek et al, 2004). Subjective responses were evaluated with the Abbreviated Profile of Hearing Aid Benefit – APHAB (Cox & Alexander, 1995), overall listener preferences for quiet and noise, and satisfaction ratings for five criteria: sound quality, appearance, retention and comfort, speech clarity and ease of use and care.

Real-Ear Occluded Response measurements showed minimal occlusion for both types of instruments in this study. Although there was more occlusion overall for RIC instruments, the difference between RIC and RITA hearing instruments was not significant. Overall maximum gain before feedback did not differ between RIC and RITA instruments. However, when analyzed by frequency, the authors found significantly greater maximum gain in the 4000-6000Hz range for RIC hearing instruments.

On the four speech tests, there were no significant differences between RITA versus RIC instruments. Furthermore, there were no significant improvements for aided listening over unaided, except for experienced users with RIC instruments on the Connected Speech Test (CST). It appears that amplification did not significantly improve scores in quiet conditions, for either instrument type, because of ceiling effects. The high unaided speech scores indicated that the subjects in this study, because of their audiometric configurations, already had broad enough access to high frequency speech cues, even in the unaided conditions. Aided performance in noise was significantly poorer than unaided on the HINT test, but no other significant differences were found for aided versus unaided conditions. This finding was in agreement with previous studies that also found degraded HINT scores for aided versus unaided conditions (Klemp & Dhar, 2008; Valente & Mispagel, 2008).

APHAB responses indicated better aided performance for both instrument types than for unaided conditions on all APHAB categories except aversiveness, in which aided performance was worse than unaided. There were no significant differences between RIC and RITA instruments. However, satisfaction ratings were significantly higher for RIC hearing instruments. New users reported more satisfaction with the appearance of RIC instruments; experienced users indicated more satisfaction with appearance, retention, comfort and speech clarity. Overall listener preferences were similar, with 80% of experienced users and 74% of new users preferring RIC instruments over RITA instruments.

The findings of Alworth and colleages are useful information for clinicians and their open-fit hearing aid candidates. Because they provided significantly more high frequency gain before feedback than RITA instruments, RIC instruments may be more appropriate for patients with significant high-frequency hearing loss. Indeed, this result may suggest that RIC instruments should be the preferred recommendation for open-fit candidates. The results of this study also underscore the importance of using subjective measures with hearing aid patients. Objective speech discrimination testing did not yield significant performance differences between RIC and RITA instruments, but participants showed significant preference for RIC instruments.

Further information is needed to compare performance in noise with RIC and RITA instruments. In this study and others, some objective scores and subjective ratings were poorer for aided conditions than unaided conditions. It is important to note that in the current study, all noise and speech was presented at a 0° azimuth angle, with directional microphones disabled. In real-life environments, it is likely that users would have directional microphones and would participate in conversations with various noise sources surrounding them. Previous work has shown significant improvements with directionality in open-fit instruments (Valente & Mispagel, 2008; Klemp & Dhar, 2008). Future work comparing directional RIC and RITA instruments, in a variety of listening environments, would be helpful for clinical decision making.

Although the performance effects and preference ratings reported here support recommendation of RIC instruments clinicians should still consider other factors when discussing options with individual patients. For instance, small ear canals may preclude the use of RIC instruments because of retention, comfort or occlusion concerns. Patients with excessive cerumen may prefer RITA instruments because of easier maintenance and care, or those with cosmetic concerns may prefer the smaller size of RIC instruments. Every patient’s individual characteristics and concerns must be considered, but the potential benefits of RIC instruments warrant further examination and may indicate that this receiver configuration should be recommended over slim-tube fittings.

References

Alworth, L.N., Plyler, P.N., Rebert, M.N., & Johstone, P.M. (2010). The effects of receiver placement on probe microphone, performance, and subjective measrues with open canal hearing instruments. Journal of the American Academy of Audiology, 21, 249-266.

Cox, R.M., & Alexander, G.C. (1995). The Abbreviated Profile of Hearing Aid Benefit. Ear and Hearing, 16, 176-186.

Cox, R.M., Alexander, G.C. & Gilmore, C. (1987). Development of the Connected Speech Test (CST). Ear and Hearing, 8, 119-126.

Hallenbeck, S.A., & Groth, J. (2008). Thin-tube and receiver-in-canal devices: there is positive feedback on both! Hearing Journal, 61(1), 28-34.

Hoen, M. & Fabry, D. (2007). Hearing aids with external receivers: can they offer power and cosmetics? Hearing Journal, 60(1), 28-34.

Klemp, E.J. & Dhar, S. (2008). Speech perception in noise using directional microphones in open-canal hearing aids. Journal of the American Academy of Audiology, 19(7), 571-578.

Kuk, F. & Baekgaard, L. (2008). Hearing aid selection and BTEs: choosing among various “open ear” and “receiver in canal” options. Hearing Review, 15(3), 22-36.

Nabelek, A.K., Tampas, J.W. & Burchfield, S.B. (2004). Comparison of speech perception in background noise with acceptance of background noise in aided and unaided conditions. Journal of Speech and Hearing Research, 47, 1001-1011.

Nilsson, M., Soli, S. & Sullivan, J. (1994). Development of the Hearing in Noise Test for the measurement of speech reception threshold in quiet and in noise. Journal of the Acoustical Society of America, 95, 1085-1099.

Pascoe, D. (1975). Frequency responses of hearing aids and their effects on the speech perception of hearing impaired subjects. Annals of Otology, Rhinology and Laryngology suppl. 23, 84: #5, part 2.

Valente, M. & Mispagel, K. (2008). Unaided and aided performance with a directional open-fit hearing aid. International Journal of Audiology, 47, 329-336.

Reviewing the benefits of open-fit hearing aids

Article of interest:

Unaided and Aided Performance with a Directional Open-Fit Hearing Aid

Valente, M., and Mispagel, K.M. (2008)

This editorial discusses the clinical implications of an independent research study. The original work was not associated with Starkey Laboratories and does not reflect the opinions of the authors. 

With the continued popularity of directional microphone use in open-fit and receiver-in-canal (RIC) hearing aids, there has been increasing interest in evaluating their performance in noisy environments. A number of studies have investigated the performance of directional, open-fit BTEs in laboratory conditions. (Valente et al., 1995; Ricketts, 2000a; Ricketts, 2000b). Some have evaluated directional microphone performance in real-life or simulated real-life noise environments (Ching et al, 2009). In the current study, the authors compared performance in omnidirectional, directional and unaided conditions using RIC instruments in R-SpaceTM (Revitt et al, 2000) recorded restaurant noise. Their goal was to obtain more externally valid results by using real-life noise in a controlled, laboratory setting.

The R-SpaceTM method involved recordings of real restaurant noise from an 8-microphone, circular array. For the test conditions, these recordings were presented through an 8-speaker, circular array to simulate the conditions in the busy restaurant. One important factor that distinguishes this study from most others is that the subjects listened to speech stimuli in the presence of noise from all directions, including the front. At the time of this study only a few other studies had tested directional microphone performance in the presence of multiple noise sources, including frontal (Ricketts, 2000a; Ricketts, 2001; Bentler et al., 2004).

The authors recruited 26 adults with no prior hearing aid experience for the study. They were fitted with binaural receiver-in-canal (RIC) instruments. The instruments were programmed without noise reduction processing and with independent omnidirectional and directional settings. Subjects were counseled on use and care of the instruments, including proper use of omnidirectional and directional programs. They returned for follow-up adjustments one week after their fitting then used their instruments for four weeks before returning for testing. Subjects were given the opportunity to either purchase the hearing aids after the study at a 50% discount or receive a $200 payment for participation.

Hearing in Noise Test (HINT) (Nilsson et al., 1994) sentence reception thresholds were obtained to evaluate sentence perception in the uncorrelated R-Space noise. The Abbreviated Profile of Hearing Aid Benefit (APHAB) (Cox & Alexander, 1995) was also administered to evaluate perceived benefit from the instruments in the study. Four APHAB subscales were evaluated independently:

– Ease of communication (EC)
– Reverberation (RV)
– Background noise (BN)
– Aversiveness to loud sounds (AV)

The authors found that subjects’ performance in the directional condition was significantly better than both omnidirectional and unaided conditions. The omnidirectional condition was not significantly better than unaided; in fact results were slightly worse than those obtained in the unaided condition.

For the APHAB results, the authors found that on the EC, RV and BV subscales, aided scores were significantly better than unaided scores. Perhaps not surprisingly, the AV score, which evaluates “aversiveness to noise” was worse in the aided conditions. The aided results combined omnidirectional and directional conditions, so it is possible that aversion to noise in omnidirectional conditions was greater than the directional conditions. However, this was not specifically evaluated in the current study.

The authors pointed out that their directional benefit, which on average was 1.7dB, was lower than those found in other studies of open-fit or RIC hearing instruments (Ricketts, 2000b; Ricketts, 2001; Bentler, 2004; Pumford et al., 2000). However, they mention that most of those studies did not use frontal noise sources in their arrays. Frontal noise sources should have obvious detrimental effects on directional microphone performance, so it is likely that the speaker arrangement in the current study affected the measured directional improvement. At the time of this publication one other study had been conducted using the R-SpaceTM restaurant noise (Compton-Conley et al 2004). They found mean directional benefits of 3.6 to 5.8 dB, but their subjects had normal hearing and the hearing aids they used were not an open-fit design and were very different from the ones in the current study..

Clinicians can gain a number of important insights from Valente and Mispagel’s study. First and foremost, directional microphones are likely to provide significant benefits for users of RIC hearing aids. At the time of publication, the authors noted that directional improvement should be studied in order to warrant the extra expense of adding directional microphones to an open-fit hearing aid order. However, most of today’s open-fit and RIC instruments already come standard with directional microphones, many of which are automatically adjustable. So there is no need to justify the use of directional microphones on a cost basis, as they usually add nothing to the hearing aid purchase price.

This study provided more evidence for directional benefit in noise, but further work is needed to determine performance differences between directional and omnidirectional microphones in quiet conditions. Dispensing clinicians should always order instruments that have omnidirectional and directional modes, whether manually or automatically adjustable. This helps ensure that the instruments will perform optimally in most situations. Even instruments with automatically adjustable directional microphones often have push-buttons that allow us to give patients additional programs. For example, a manually accessible, directional program, perhaps with more aggressive noise reduction, offers the user another option for excessively noisy situations.

The current study obtained slightly reduced directional effects compared to other studies that tested subjects in speaker arrays without frontal noise sources. This underscores the importance of counseling patients about proper positioning when using directional settings. In general, patients should understand that they will be better off when they can put as much noise behind them as possible. But, it is also important to ensure that patients have reasonable expectations about directional microphones. They must understand that the directional microphone will help them focus on conversation in front of them, but will not completely remove competing noise behind them. Patients must also understand that omnidirectional settings are likely to offer no improvement in noise and might even be a detriment to speech perception in some noisy environments.

Subjects in Valente and Mispagel’s study were offered the opportunity to purchase their hearing instruments at a 50% discount after the study’s completion. Only 8 of the 26 subjects opted to do so. Of the remaining subjects, 3 reported that the perceived benefit was not enough to justify the purchase, whereas 15 subjects did not report any significant perceived benefit. This leads to another important point about patient counseling.

The subjects in this study, like most candidates for open-fit or RIC instruments, had normal low-frequency hearing. Therefore, they may have had less of a perceived need for hearing aids in the first place. It is important for audiologists to discuss realistic expectations and likely hearing aid benefits with patients in detail at the hearing aid selection appointment, before hearing aids are ordered. Patients who are unmotivated or do not perceive enough need for hearing assistance will ultimately be less likely to perceive significant benefit from their hearing aids. This is particularly true in everyday clinical situations, in which patients are not typically offered a 50% discount and will have to factor financial constraints into their decisions. For most open-fit or RIC candidates, their motivation and perceived handicap will be related to their lifestyle: their social activities, employment situation, hobbies, etc. Because a patient who has a less than satisfying experience with hearing aids may be reluctant to pursue them again in the future, it is critical for the clinician to help them establish realistic goals early on, before hearing aid options are discussed.

References
Bentler, R., Egge, J., Tubbs, J., Dittberner, A., and Flamme, G. (2004). Quantification of directional benefit across different polar response patterns. Journal of the American Academy of Audiology 15(9), 649-659.

Ching, T.C., O’Brien, A., Dillon, H., Chalupper, J., Hartley, L., Hartley, D., Raicevich, G., and Hain, J. (2009). Journal of Speech, Language and Hearing Research 52, 1241-1254.

Compton-Conley, C., Neuman, A., Killion, M., and Levitt, H. (2004). Performance of directional microphones for hearing aids: real world versus simulation. Journal of the American Academy of Audiology 15, 440-455.

Cox, R.M. and Alexander, G.C. (1995). The abbreviated profile of hearing-aid benefit. Ear and Hearing 16, 176-183.

Nilsson, M., Soli, S. and Sullivan, J. (1994). Development of the hearing in noise test for the measurement of speech reception thresholds in quiet and in noise. Journal of the Acoustical Society of America 95, 1085-1099.

Pumford, J., Seewald, R,. Scollie, S. and Jenstad, L. (2000). Speech recognition with in-the-ear and behind-the-ear dual microphone hearing instruments. Journal of the American Academy of Audiology 11, 23-35.

Revit, L., Schulein, R., and Julstrom, S. (2002). Toward accurate assessment of real-world hearing aid benefit. Hearing Review 9, 34-38, 51.

Ricketts, T. (2000a). The impact of head angle on monaural and bilateral performance with directional and omnidirectional hearing aids. Ear and Hearing 21, 318-329.

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

Ricketts, T., Lindley, G., and Henry, P. (2001). Impact of compression and hearing aid style on directional hearing aid benefit and performance. Ear and Hearing 22, 348-360.

Valente, M., Fabry, D., and Potts, L. (1995). Recognition of speech in noise with hearing aids using a dual microphone. Journal of the American Academy of Audiology 6, 440-449.

Valente, M., & Mispagel, K.M. (2008). Unaided and aided performance with a directional open-fit hearing aid. International Journal of Audiology, 47, 329-336.