Hearing Impairment Simulator Based on Auditory Excitation Pattern Playback: WHIS

A new version of the Wakayama-University Hearing Impairment Simulator (WHIS) was developed based on the idea of auditory excitation pattern (EP) playback instead of direct simulation of loudness recruitment in conventional methods. The EPs of normal hearing (NH) and hearing impaired (HI) listeners were computed using a frame-based version of the gammachirp filterbank (GCFB), in which the cochlear input-output (IO) function was controlled by a parameter called the compression health
$\alpha $
. WHIS synthesizes simulated hearing loss (HL) sounds to make the EPs of an NH listener sufficiently close to the EPs of a target HI listener by applying active and passive level reduction to the input signals. Active reduction can be simply formulated as the composite function of the IO function of HI and the inverse NH IO function of NH. Passive reduction was determined to maintain the hearing level shown in the audiogram of the HI listener. Two methods were proposed for sound synthesis: a direct time-varying filter method and a filterbank analysis-synthesis method. WHIS was compared with a Cambridge version of the HL simulator (CamHLS) in terms of differences in the IO functions and spectral distances in the EP spectrograms. WHIS yielded smaller distances than CamHLS, suggesting that EP playback is an effective method for HL simulations.