The industrial aspect in describing performance characteristics in complex hearing aids

Performance characteristics of complex hearing aids (e.g. AGC hearing aids) which are measured and presented using existing standards (IEC 118) may mislead the hearing aid fitter. In this paper examples of possible erroneous interpretations of frequency response curve are demonstrated. A test method is proposed to record "instantaneous frequency response" -- the actual response in the AGC mode which corresponds to the perceived tonal balance.