The most important element in a hearing aid fitting is the OSPL90. This, according to ANSI 3.22, is the maximum sound that can be transduced with a 90 dB SPL input. The OSPL90 is a well-defined measure that provides information on the maximum output, and when combined with other measuring tools such as the Real Ear Coupler Difference (RECD) can provide precise estimates of the sound level that is generated in an ear canal. Overly high sound levels can generate further permanent sensory hearing loss and is the primary reason why hard of hearing consumers reject their hearing aids.
In some sense, I am much more “casual” about the other elements in a hearing aid prescription such as gain and frequency response. These can be changed at any time to improve the sound quality, speech intelligibility, or musical tone and indeed are frequently altered at subsequent check-up appointments based on a range of comments and of object measures. But the OSPL90 remains the same- too high and one risks further permanent hearing loss, and too low, the speech and music signals are less than optimal.
In the terminology of the PCAST report, “basic” hearing aids may be sold over the counter by-passing the expertise and training of an audiologist. Even “basic” hearing aids can have OSPL90 levels that are set too high.
PSAPs and OSPL90
And what about Personal Amplification Sound Products or PSAPs. Getting rid of the PSAP category (defined by the FDA in 2009) and lumping everything together as a “basic” hearing aid would increase access to hearing aids. I cannot really argue against this since many PSAPs can generate identical gains, and maximum outputs as many commercially available hearing aids, but lumping PSAPs together with “basic” hearing aids that may be useful for those hard of hearing people with mild to moderate hearing losses doesn’t solve the issue.
Whether a hearing aid is a PSAP or a “basic” hearing aid, the OSPL90 can still be set to be too high. Without verification of any fitting (whether it is an over the counter device or a prescribed hearing aid by an audiologist), there is a risk of creating further permanent hearing loss. This has nothing to do with a hearing loss being a mild or a moderate one.
And what about music?
Well for this we need to be reminded of the work of Brian Fligor. Dr. Fligor has done some nice work over the last 20 years (he’s still quite young) on the use of “after-market” technologies. Specifically he was able to show that the same music, on the same volume control, and on the same MP3 player could generate output levels that were as much as 20 dB different, depending on which earphone you used. For example, on volume 6/10, with one earphone the output was 85 dBA and with another earphone, the output was 105 dBA- one potentially damaging, and the other not. The MP3 was identical and the music was identical…only the earphone was changed.
Whether one will be listening to their favorite music via a “hearable”- any wireless headset – or a hearing aid (basic or otherwise), the output can be significantly altered with “after-market” earphones.
Removing the prescription (and all that implies) for “basic” hearing aids from the audiologist is silly. There is no science to support this. While I appreciate improved access, the recommendations of the PCAST committee are simplistic and ill-founded.
Perhaps next time, this committee with have some audiologists and other industry personnel on board?
