Characterization and simulation of impaired hearing: implications for hearing aid design

This article reviews several aspects of auditory perception that are affected by hearing loss of cochlear origin. It is argued that most of the observed effects can be understood in terms of damage to a physiologically vulnerable active process in the cochlea. In a normal ear, this process enhances sensitivity and frequency selectivity and reduces the slope of the input-output function on the basilar membrane. Damage to the active process in impaired ears leads to reduced sensitivity and frequency selectivity, an abnormally rapid rate of growth of loudness with intensity, reduced temporal integration and, for certain types of stimuli, reduced temporal resolution. The implications and relevance of each of these effects to the design and fitting of hearing aids are discussed.