SNR-based intelligibility models require imposed floor and ceiling limits.

Evidence

Some SNR floors and ceilings must exist, such that intelligibility would not be influenced by varying the SNR above or below these limits. Several speech intelligibility models are based on SNRs computations in frequency bands (Rhebergen and Versfeld 2005 ; Beutelmann et al. 2010 ; Collin and Lavandier 2013 ). In the presence of amplitude-modulated or filtered noise, these models could compute infinite SNRs, and then conduct to infinite intelligibility. In order to keep the predictions realistic, a limitation of SNRs must be introduced. Collin and Lavandier ( 2013 ) proposed a 10-dB ceiling limit in their model. Other models for intelligibility in modulated noise (Rhebergen and Versfeld 2005 ; Beutelmann et al. 2010 ) are based on the speech intelligibility index (SII) calculation (ANSI S3.5 1997 ) which adopts the SNR values of ‑15 dB and + 15 dB as floor and ceiling limits respectively. This range has its origins in the work of Beranek ( 1947 ) who reported that the total dynamic range of speech is about 30 dB (in any frequency band) by interpreting the short-term speech spectrum measurements reported by Dunn and White ( 1940 ). — Dijk, Pim van, Physiology, Psychoacoustics and…, 3536

Categorization

• DEFINE: Explains what the -15/+15 dB floor and ceiling in the SII standard are and where they come from.