Audible circuit noise in hearing aid amplifiers.

Audible electronic circuit noise generated within a hearing aid is distracting to a listener in quiet situations and, if the noise level is high enough, may cause listener irritation and rejection of the hearing aid. Thus for hearing aid specification and fitting purposes, it is useful to know the acoustic levels at which this internal noise may become audible and also at which it may become objectionable. For hearing aid amplifier circuit specification and design purposes, it is useful to know the same levels in electrical terms. This paper reports on a study that used an amplifier with no acoustic input and a hearing aid receiver output to simulate internally generated hearing aid circuit noise. Results are reported for testing eight subjects with high-frequency hearing loss for the perceived acoustic and electrical levels at which internal circuit noise became both audible and objectionable.