Broader cochlear filtering reduces low-frequency noise fluctuations, explaining lost masking release
Evidence
In contrast, it was found that CI users showed no difference in speech intelligibility between maskers with and without inherent envelope fluctuations. Here, these initial findings in CI users were extended to listeners with cochlear hearing loss and the results were compared with those from normal-hearing listeners at either equal sensation level or equal sound pressure level. The results from hearing-impaired listeners (and in normal-hearing listeners at high sound levels) are consistent with a relative reduction in low-frequency inherent noise fluctuations due to broader cochlear filtering. The reduced effect of inherent temporal fluctuations in noise, due to either current spread (in CI users) or broader cochlear filters (in hearing-impaired listeners), provides a new way to explain the loss of masking release experienced in CI users and hearing-impaired listeners when additional amplitude fluctuations are introduced in noise maskers. — Dijk, Pim van, Physiology, Psychoacoustics and…, 2161
Recent studies in normal-hearing listeners have used envelope-vocoded stimuli to show that the masking of speech by noise is dominated by the temporal-envelope fluctuations inherent in noise, rather than just overall power. Because these studies were based on vocoding, it was expected that cochlear-implant (CI) users would demonstrate a similar sensitivity to inherent fluctuations. In contrast, it was found that CI users showed no difference in speech intelligibility between maskers with and without inherent envelope fluctuations. Here, these initial findings in CI users were extended to listeners with cochlear hearing loss and the results were compared with those from normal-hearing listeners at either equal sensation level or equal sound pressure level. The results from hearing-impaired listeners (and in normal-hearing listeners at high sound levels) are consistent with a relative reduction in low-frequency inherent noise fluctuations due to broader cochlear filtering. The reduced effect of inherent temporal fluctuations in noise, due to either current spread (in CI users) or broader cochlear filters (in hearing-impaired listeners), provides a new way to explain the loss of masking release experienced in CI users and hearing-impaired listeners when additional amplitude fluctuations are introduced in noise maskers. — Dijk, Pim van, Physiology, Psychoacoustics and…, 2161
Categorization
- XREF: Explains the loss of masking release — connects to the psychoacoustics of comodulation masking release in normal vs impaired cochleae. — connects to: Reducing audible fluctuations in a masker lowers post-masked thresholds by up to 24 dB — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 570; Hearing-impaired listeners fail to gain temporal resolution in background noise — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1933; Missing efferent benefits may explain cochlear-implant users’ speech-in-noise deficits — Dijk, Pim van, Physiology, Psychoacoustics and…, 1939 (+12 more)
- QUESTION: Worth chasing: does broader filtering physically smooth low-frequency envelope fluctuations, and at what channel widths does the effect kick in?
- corroborated: 5 independent passages support this claim — Dijk, Pim van, Physiology, Psychoacoustics and…, 2161