Simulations with FADE of the effect of impaired hearing on speech recognition performance cast doubt on the role of spectral resolution.

Listeners with hearing impairment show sub-optimal processing of acoustic signals which affects their ability to recognize speech. In this contribution, three effective signal processing deficits are proposed to simulate sensorineural hearing impairment and their effect on simulated speech recognition performance is studied. Psychoacoustic and speech recognition experiments were simulated with the framework for auditory discrimination experiments (FADE). Loss in absolute hearing threshold was modeled as lower level limit, supra-threshold loss in envelope amplitude resolution as multiplicative noise, and reduced spectral resolution was simulated with an increase of the analysis bandwidth. Their effects on the speech recognition performance with the German matrix test in quiet and noise, the audiogram, and tone in (notched) noise detection experiments were systematically examined. The simulations indicate that each psychoacoustic experiment relates to at least one signal processing deficit. This indicates the possibility to determine individual model parameters from the outcome of psychoacoustic experiments. Moreover, absolute hearing thresholds yield the highest effects on simulated speech recognition thresholds, followed by supra-threshold loss in envelope amplitude resolution, and-to a much smaller degree-spectral resolution. A reduced spectral resolution only affected recognition performance in fluctuating masker for normal hearing thresholds, indicating its potential relevance for more complex listening conditions. In contrast to popular interpretations in the literature, the simulations reveal that reduced spectral resolution plays a minor role compared to a reduced envelope amplitude resolution in characterizing supra-threshold hearing loss at least in stationary noise.