Compensation for recruitment of loudness in sensorineural hearing impairments using a sinusoidal model of speech

The problem of compensation for a particular form of sensorineural hearing impairment known as recruitment of loudness is explored. The technique used is based on a digital sinusoidal analysis/synthesis model of speech. Time-varying, frequency-dependent nonlinearities are applied between the analysis and synthesis modules to perform the compensation. This system differs from traditional multichannel filtering techniques by incorporating a model of the interaction of sinusoidal maskers in both normal-hearing and hearing-impaired individuals. Such phenomena as spread of masking, elevated thresholds, reduced dynamic range, and other psychoacoustic properties are taken into account in the compensation. A system of simultaneous equations is solved to determine the proper gains for each sinusoid. The net effect is a combination between multichannel amplitude compression and automatic gain control since the compressive gains calculated separately for each frame of speech automatically adjust to the level of the speech components in that frame. A simplified version of the compensation algorithm has been implemented in near real-time using a Texas Instruments TMS320C30-based microprocessor board within a personal computer