Mead C. Killion
Etymotic Res., 61 Martin Lane, Elk Grove Village, IL 60007
At one time, most of the things known about hearing aids were wrong. The resulting hearing aid designs often made it more difficult to hear in noise rather than less: In 1970, Tillman et al. reported a 20-dB degradation in the signal-to-noise ratio corresponding to a 50% word-recognition score. The situation has improved because of improved components and especially because of an improved understanding of what a hearing aid can do to help [or make things worse, such as ``filtering out the noise,'' which unavoidably results in the loss of valuable speech cues as well (Villchur, 1993)]. Most modern hearing aids can provide improved hearing in noise, and some of them can handle high-level noise and music without audible distortion. One design is being successfully used in concerts by members of major symphonies. Nonetheless, even the best---and best fitted---hearing aids typically leave their wearer with a deficit of at least 2--3 dB in tolerable signal-to-noise ratio (mild-moderate loss), often 6--8 dB (moderate loss), and sometimes much more. Objective improvements in signal-to-noise ratio appear needed to close the gap.