Speech intelligibility for target and masker with different spectra

Thibaud Leclère*, David Théry, Mathieu Lavandier, John F. Culling

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference proceeding contributionpeer-review

5 Citations (Scopus)
10 Downloads (Pure)


The speech intelligibility index (SII) calculation is based on the assumption that the effective range of signal-to-noise ratio (SNR) regarding speech intelligibility is [− 15 dB; +15 dB]. In a specific frequency band, speech intelligibility would remain constant by varying the SNRs above + 15 dB or below − 15 dB. These assumptions were tested in four experiments measuring speech reception thresholds (SRTs) with a speech target and speech-spectrum noise, while attenuating target or noise above or below 1400 Hz, with different levels of attenuation in order to test different SNRs in the two bands. SRT varied linearly with attenuation at low-attenuation levels and an asymptote was reached for high-attenuation levels. However, this asymptote was reached (intelligibility was not influenced by further attenuation) for different attenuation levels across experiments. The − 15-dB SII limit was confirmed for highpass filtered targets, whereas for low-pass filtered targets, intelligibility was further impaired by decreasing the SNR below − 15 dB (until − 37 dB) in the high-frequency band. For high-pass and low-pass filtered noises, speech intelligibility kept improving when increasing the SNR in the rejected band beyond + 15 dB (up to 43 dB). Before reaching the asymptote, a 10-dB increase of SNR obtained by filtering the noise resulted in a larger decrease of SRT than a corresponding 10-dB decrease of SNR obtained by filtering the target (the slopes SRT/attenuation were different depending on which source was filtered). These results question the use of the SNR range and the importance function adopted by the SII when considering sharply filtered signals.

Original languageEnglish
Title of host publicationPhysiology, psychoacoustics and cognition in normal and impaired hearing
EditorsPim van Dijk, Deniz Başkent, Etienne Gaudrain, Emile de Kleine, Anita Wagner, Cris Lanting
Place of PublicationCham
PublisherSpringer, Springer Nature
Number of pages10
ISBN (Electronic)9783319254746
ISBN (Print)9783319254722
Publication statusPublished - 2016
Externally publishedYes
EventInternational Symposium on Hearing (17th : 2015) - Groningen, Netherlands
Duration: 15 Jun 201519 Jun 2015

Publication series

NameAdvances in experimental medicine and biology
ISSN (Print)0065-2598
ISSN (Electronic)2214-8019


ConferenceInternational Symposium on Hearing (17th : 2015)

Bibliographical note

Copyright the Author(s) 2016. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.


  • speech intelligibility index
  • speech in noise
  • speech intelligibility measurement


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