Band importance for sentences and words reexamined

Abstract

Band-importance functions were created using the "compound" technique [Apoux and Healy, J. Acoust. Soc. Am. 132, 1078-1087 (2012)] that accounts for the multitude of synergistic and redundant interactions that take place among speech bands. Functions were created for standard recordings of the speech perception in noise (SPIN) sentences and the Central Institute for the Deaf (CID) W-22 words using 21 critical-band divisions and steep filtering to eliminate the influence of filter slopes. On a given trial, a band of interest was presented along with four other bands having spectral locations determined randomly on each trial. In corresponding trials, the band of interest was absent and only the four other bands were present. The importance of the band of interest was determined by the difference between paired band-present and band-absent trials. Because the locations of the other bands changed randomly from trial to trial, various interactions occurred between the band of interest and other speech bands which provided a general estimate of band importance. Obtained band-importance functions differed substantially from those currently available for identical speech recordings. In addition to differences in the overall shape of the functions, especially for the W-22 words, a complex microstructure was observed in which the importance of adjacent frequency bands often varied considerably. This microstructure may result in better predictive power of the current functions.

Band importance functions of listeners with cochlear implants using clinical maps

“…As shown, BIFs varied substantially across listeners, with no evident trend in BIF shape. As expected based on previous studies in listeners with normal hearing (Healy et al, 2013), most listeners with cochlear implants had channels with high importance (i.e., high log odds) in the 1-2 kHz region. However, many also appear to rely heavily on lower frequency channels, in the region of 200-400 Hz.…”

“…Average BIFs in large populations of listeners with normal hearing are consistent across subjects (Healy et al, 2013). However, listeners with cochlear implants are unlikely to demonstrate similar consistency.…”

“…Several alternative methods have been devised to address this issue. One approach is to simply randomize the combination of bands presented with or without the target band (Apoux and Healy, 2012;Healy et al, 2013), to average band importance for the target band across all potential interactions with other bands. Others have removed individual bands from the spectrum, to observe the loss in intelligibility due to the missing information (Henry et al, 2000;Sladen and Ricketts, 2015).…”

Talker effects in speech band importance functions

“…In contrast to the speech-material effect, there is reason to believe that the compound method is highly sensitive to acoustic characteristics of the particular talker used to create the speech recordings --Reasonable correspondence was observed between prominent peaks in the band-importance functions and the frequencies of the individual talkers' first three formants in Healy, Yoho, and Apoux (2013). The current experiment supports the existence of a talker effect by indicating that microstructure is reduced when a single talker is replaced by a multi-talker set.…”

Learning an intelligibility map of individual utterances

“…The work in [4] investigated the importance of individual frequency bands to the intelligibility of words in the context of randomly selected subsets of other frequency bands. It shows that while this importance is quite stable across listeners, it varies a great deal across recordings.…”