Effects of Noise Reduction on AM Perception for Hearing-Impaired Listeners

Abstract

Noise reduction (NR) systems are commonplace in modern digital hearing aids. Though not improving speech intelligibility, NR helps the hearing-aid user in terms of lowering noise annoyance, reducing cognitive load and improving ease of listening. Previous psychophysical work has shown that NR does in fact improve the ability of normal-hearing (NH) listeners to discriminate the slow amplitude-modulation (AM) cues representative of those found in speech. The goal of this study was to assess whether this improvement of AM discrimination with NR can also be observed for hearing-impaired (HI) listeners. AM discrimination was measured at two audio frequencies of 500 Hz and 2 kHz in a background noise with a signal-to-noise ratio of 12 dB. Discrimination was measured for ten HI and ten NH listeners with and without NR processing. The HI listeners had a moderate sensorineural hearing loss of about 50 dB HL at 2 kHz and normal hearing (≤ 20 dB HL) at 500 Hz. The results showed that most of the HI listeners tended to benefit from NR at 500 Hz but not at 2 kHz. However, statistical analyses showed that HI listeners did not benefit significantly from NR at any frequency region. In comparison, the NH listeners showed a significant benefit from NR at both frequencies. For each condition, the fidelity of AM transmission was quantified by a computational model of early auditory processing. The parameters of the model were adjusted separately for the two groups (NH and HI) of listeners. The AM discrimination performance of the HI group (with and without NR) was best captured by a model simulating the loss of the fast-acting amplitude compression applied by the normal cochlea. This suggests that the lack of benefit from NR for HI listeners results from loudness recruitment.

Double-pass consistency for amplitude- and frequency-modulation detection in normal-hearing listeners

“…The present study was conducted with young normalhearing participants. Some studies aiming to model AM detection and discrimination for elderly listeners and listeners with sensorineural hearing loss suggest that the variance of the additive internal noise may increase substantially (up to a factor 6-10) because of aging and cochlear lesions (Derleth et al, 2001;Ives et al, 2014;Paraouty et al, 2016;Wallaert et al, 2017Wallaert et al, , 2018. From a behavioral perspective, this increase in internal noise should yield a decrease in the consistency of the responses of elderly and hearingimpaired persons, as measured in the current double-pass paradigm.…”