Clinical results of hearing aid with noise-level-controlled selective amplification.

We have developed a hearing aid which reduces the low-frequency energy of the input sound according to the input noise level and the spectrum of the environmental noise. The results of speech discrimination tests using speech in noise in 70 hearing-impaired subjects showed improvement in word discrimination scores in noise of over 15% for 50 of 53 subjects with sensorineural hearing loss. This group of hearing-impaired patients was subdivided into categories according to (a) audiogram type [flat, sloping (i.e. gradual high-frequency loss) and abruptly falling (steep high-frequency slope)]; (b) degree of hearing loss (less than or more than 50 dB average loss) and (c) etiology (familial deafness, presbyacusis). Results on 17 subjects with conductive or mixed hearing impairments showed no improvement, but expressed a preference for this system. The subject reported that the sound was more natural and quiet compared with the conventional AGC hearing aids.