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On detectable and meaningful speech-intelligibility benefits

Whitmer, William M.; McShefferty, David; Akeroyd, Michael A.



The most important parameter that affects the ability to hear and understand speech in the presence of background noise is the signal-to-noise ratio (SNR). Despite decades of research in speech intelligibility, it is not currently known how much improvement in SNR is needed to provide a meaningful benefit to someone. We propose that the underlying psychophysical basis to a meaningful benefit should be the just noticeable difference (JND) for SNR. The SNR JND was measured in a series of experiments using both adaptive and fixed-level procedures across participants of varying hearing ability. The results showed an average SNR JND of approximately 3 dB for sentences in same-spectrum noise. The role of the stimulus and link to intelligibility was examined by measuring speech-intelligibility psychometric functions and comparing the intelligibility JND estimated from those functions with measured SNR JNDs. Several experiments were then conducted to establish a just meaningful difference (JMD) for SNR. SNR changes that could induce intervention-seeking behaviour for an individual were measured with subjective scaling and report, using the same stimuli as the SNR JND experiment as pre- and post-benefit examples. The results across different rating and willingness-to-change tasks showed that the mean ratings increased near linearly with a change in SNR, but a change of at least 6 dB was necessary to reliably motivate participants to seek intervention. The magnitude of the JNDs and JMDs for speech-intelligibility benefits measured here suggest a gap between what is achievable and what is meaningful.


Whitmer, W. M., McShefferty, D., & Akeroyd, M. A. (in press). On detectable and meaningful speech-intelligibility benefits. Advances in Experimental Medicine and Biology, 894,

Journal Article Type Article
Acceptance Date Dec 1, 2015
Online Publication Date Apr 15, 2016
Deposit Date Nov 16, 2016
Publicly Available Date Nov 16, 2016
Journal Advances in Experimental Medicine and Biology
Electronic ISSN 0065-2598
Publisher Springer Verlag
Peer Reviewed Peer Reviewed
Volume 894
Keywords Signal-to-noise ratio, Just-noticeable difference, Speech intelligibility, Hearing impairment
Public URL
Publisher URL
Additional Information Physiology, Psychoacoustics and Cognition in Normal and Impaired Hearing / editors, Hearing. Editors: Pim van Dijk,
Deniz Baskent, Etienne Gaudrain, Emile de Kleine, Anita Wagner, Cris Lanting. ISBN 9783319254746.


chp%3A10.1007%2F978-3-319-25474-6_47.pdf (1.1 Mb)

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