Gain-induced speech distortions and the absence of intelligibility benefit with existing noise-reduction algorithms
- Authors
- Kim, G.; Loizou, P.C.
- Issue Date
- 2011
- Citation
- Journal of the Acoustical Society of America, v.130, no.3, pp.1581 - 1596
- Journal Title
- Journal of the Acoustical Society of America
- Volume
- 130
- Number
- 3
- Start Page
- 1581
- End Page
- 1596
- URI
- http://scholarworks.bwise.kr/ssu/handle/2018.sw.ssu/14497
- DOI
- 10.1121/1.3619790
- ISSN
- 0001-4966
- Abstract
- Most noise-reduction algorithms used in hearing aids apply a gain to the noisy envelopes to reduce noise interference. The present study assesses the impact of two types of speech distortion introduced by noise-suppressive gain functions: amplification distortion occurring when the amplitude of the target signal is over-estimated, and attenuation distortion occurring when the target amplitude is under-estimated. Sentences corrupted by steady noise and competing talker were processed through a noise-reduction algorithm and synthesized to contain either amplification distortion, attenuation distortion or both. The attenuation distortion was found to have a minimal effect on speech intelligibility. In fact, substantial improvements (> 80 percentage points) in intelligibility, relative to noise-corrupted speech, were obtained when the processed sentences contained only attenuation distortion. When the amplification distortion was limited to be smaller than 6 dB, performance was nearly unaffected in the steady-noise conditions, but was severely degraded in the competing-talker conditions. Overall, the present data suggest that one reason that existing algorithms do not improve speech intelligibility is because they allow amplification distortions in excess of 6 dB. These distortions are shown in this study to be always associated with masker-dominated envelopes and should thus be eliminated. © 2011 Acoustical Society of America.
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