Gain, frequency response, and maximum output requirements for hearing aids

This article applies the gain and frequency response and maximum output selection procedures currently recommended by the National Acoustic Laboratories (NAL) of Australia to the audiograms of a representative group of adult and child clients of Australian Hearing Services (AHS) to specify the performance that is required of various types of hearing aids in order to ensure that they can provide adequate gain, frequency response, and maximum output levels for at least 90% of the AHS client population. Cumulative frequency distributions of required 2-cc coupler gain slopes were calculated for each type of aid and used to design required frequency response variations. Coupler slope requirements in different octaves were found to be independent of one another. The required range of gain-maximum output combinations was determined for each type of aid.