Article of interest:
An Electroacoustic Analysis of Over-the-Counter Hearing Aids
Callaway, S.L., and Punch, J.L. (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.
Hearing-impaired individuals have a variety of amplification options available to them. Audiologists help patients select the most appropriate hearing aids based on their hearing loss, lifestyle and listening needs, manual dexterity and a number of other factors. Financial constraints are often a consideration as well, so hearing aid manufacturers offer a wide selection of circuit types, including some more basic, economical choices.
In today’s economy, consumers seem more concerned than ever about hearing aid cost. Not surprisingly, there has been an increase in the availability of inexpensive, over-the-counter (OTC) hearing devices. The price of an OTC instrument can range from under $50 to several hundred dollars each. While some of these devices might fit the FDA definition of “hearing aids” (FDA, 2007a; S874.3300), their distribution often does not meet FDA requirements. For instance, the FDA requires a person buying a hearing aid to be examined by a physician to rule out medical contraindications and a medical waiver must be signed if they choose not to obtain medical clearance. Most OTC devices are purchased in a retail store or over the internet, so the consumer never interacts with an audiologist and may never be asked for proof of medical clearance. Indeed, the authors of the current study found only one OTC manufacturer that asked consumers to sign a medical waiver prior to purchase.
Despite the decidedly non-clinical distribution of most OTC hearing devices, many audiologists have encountered them, either through advertising or via a patient who has purchased one before coming to our office. Because we recognize the importance of proper diagnosis, selection, fitting verification and follow-up care, most audiologists have significant reservations about the safety and quality of OTC devices.
These concerns appear to be well founded. The current authors found only one OTC manufacturer that required consumers to submit an audiogram or select an audiometric profile when purchasing an instrument. When they contacted customer service for several OTC manufacturers, they found that representatives had very little knowledge of the technical characteristics of their devices and were unwilling or unable to provide instrument specifications. Previous research has shown that some OTC devices over-amplify in the low frequencies and that only reverse-slope hearing losses could be suitably fitted (Cheng & McPherson, 2000).
There is a need for more information about the performance of OTC hearing devices so that audiologists can counsel patients about potential benefits and limitations. In the current study, Callaway and Punch examined electroacoustic characteristics of eleven OTC hearing devices. The selected OTC instruments were categorized into two groups: low-cost devices priced from $10 to $73 and mid-range devices priced from $349 to $495. The low-cost devices were behind-the-ear, receiver-in-canal style or in-the-canal style. The mid-range devices were in-the-ear or in-the-canal styles.
Technical specification sheets were obtained from the manufacturers of the mid-range devices, but the authors found that specifications for low-cost devices were either unreliable or unavailable. Therefore, they purchased all of the low-cost devices and conducted their own electroacoustic measurements (ANSI 1987, 1996). Tests were conducted twice, two months apart, to ensure reliability and validity of the data. Two of the low-range devices were excluded because they were not working at the time of the second round of testing.
The authors compared NAL-R prescribed gain and output targets (Byrne & Dillon, 1986; Dillon, 2001) to actual gain and outputs measured from the OTC hearing devices. In order to be deemed acceptable for a particular audiometric configuration, gain was required to be within +/-12dB of the NAL targets and output was required to be between -5dB and +3dB of the target. The frequency range was required to provide measurable gain between 250 to 6000Hz.
Overwhelmingly, Callaway and Punch found that OTC devices had more gain in the low-frequencies than in the high-frequencies. In fact, all of the low-cost devices were classified as “special purpose” devices because of their low-frequency emphasis and as a result had to be tested using lower three-frequency averages. Total harmonic distortion was within tolerance for all but one OTC instrument, but equivalent input noise was often well above ANSI standards. Only two of the devices, both mid-range devices, had acceptable frequency responses from 250-6000Hz. Most frequency responses were peaked rather than smooth, with some peaks as high as 15dB in the range of 1000Hz to 5000Hz.
Gain and output measures yielded variable results across audiometric configurations for low-cost and mid-range OTC instruments Because so many of the OTC devices over-amplified in the low frequencies, gain targets for the mild-sloping hearing loss configuration were not met, but the flat-moderate hearing loss targets were met more easily. The moderate-sloping loss was the poorest fit, especially for low-cost instruments, primarily because they were unable to provide adequate gain for high frequencies.
The authors concluded that the low-cost instruments were inadequate for use by hearing-impaired individuals, because of over-amplification in low frequencies, inadequate high-frequency amplification, high input noise, and narrow frequency response. These conclusions are supported by previous research (Killion, 2003). However, the mid-range instruments had gain and output characteristics that were somewhat more like traditional hearing instruments. Therefore, they could potentially be considered an acceptable low-cost solution for consumers who cannot afford traditional hearing aids dispensed by a hearing care professional. Of course, any of these instruments are more likely to help if consumers are asked to submit recent audiograms or choose an audiometric profile before purchase.
The findings in this study corroborate the concerns many audiologists have about the performance of over-the-counter hearing devices, especially low-cost instruments. In addition to the adverse effects of a reverse-sloping, narrow frequency response, high output levels and frequency response peaks are likely to cause many users of OTC instruments to turn their devices down in order to avoid discomfort or feedback. The resulting reduction in gain would thereby fall even farther below required levels. Because these devices cannot be programmed to an individual’s prescribed settings, most users would likely be forced to choose between inadequate gain or discomfort and feedback.
The cost of many OTC hearing devices is low enough that consumers only take a small financial risk if they choose to purchase. However, individuals in need of hearing assistance, having been disappointed with the performance of OTC aids, might assume that appropriately prescribed hearing instruments, fitted and verified by an audiologist, would be no better.
An additional concern regarding the use of OTC products is the fact that purchasers do not get a thorough diagnostic evaluation, nor do they receive recommendations from a qualified hearing care professional. Consumers who forgo a complete audiogram prior to purchasing a hearing device are not referred for appropriate consultation with a physician if they have medical contraindications to hearing aid use or symptoms that require further diagnostic study.
More information about OTC hearing devices is needed, as well as stricter regulation to define and classify them and enforce their proper distribution. More rigorous guidelines should be established to ensure their safety and performance. However, it is also incumbent upon audiologists as hearing care professionals to educate patients about the importance of prescriptive fitting and follow-up care and to guide them to make appropriate decisions about their amplification needs. Over-the-counter hearing devices are bound to appeal to cost-conscious hearing-impaired individuals. Audiologists must be familiar with the limitations and potential risks of OTC devices and be prepared to discuss them with patients.
American National Standards Institute (1987). Specification of hearing aid characteristics (ANSI S3.22-1987). New York: Author.
American National Standards Institute (1996). Specification of hearing aid characteristics (ANSI S3.22-1966). New York: Author.
Byrne, D. & Dillon, H. (1986). The National Acoustic Laboratories’ (NAL) new procedure for selecting the gain and frequency response of a hearing aid. Ear & Hearing, 7, 257-265.
Callaway, S.L., and Punch, J.L. (2008). An Electroacoustic Analysis of Over-the-Counter Hearing Aids. American Journal of Audiology, 17,14-24.
Cheng, C.M., & McPherson, B. (2000). Over-the-counter hearing aids: Electroacoustic characteristics and possible target client groups. Audiology, 39(2), 110-116.
Dillon, H. (2001). Hearing aids. New York: Thieme.
Killion, M. (2003). Citizen petition to the Food and Drug Administration, August 7, 2003. Petition #2003P-0362. Retrieved from www.fda.gov/ohrms/dockets/dailys/03/aud03/081203/03p-0362-cp00001-vol1.pdf.
McPherson, B., & Wong, E.T.L. (2005). Effectiveness of an affordable hearing aid with elderly persons. Disability and Rehabilitation, 27, 601-609.
Parving, A., Christensen, B., Nielsen, J., & Konradsson, K. (2005). Clinical trial of low-cost, high power compression hearing aid. Audiological Medicine, 3(2), 76-81.
U.S. Food and Drug Administration, (2007a). Subpart D – prosthetic devices. Retrieved May 6, 2007, from www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch. 21:18.104.22.168.23.4.