Using speech sounds to test functional spectral resolution in listeners with cochlear implants

Abstract

In this study, spectral properties of speech sounds were used to test functional spectral resolution in people who use cochlear implants (CIs). Specifically, perception of the /ba/-/da/ contrast was tested using two spectral cues: Formant transitions (a fine-resolution cue) and spectral tilt (a coarse-resolution cue). Higher weighting of the formant cues was used as an index of better spectral cue perception. Participants included 19 CI listeners and 10 listeners with normal hearing (NH), for whom spectral resolution was explicitly controlled using a noise vocoder with variable carrier filter widths to simulate electrical current spread. Perceptual weighting of the two cues was modeled with mixed-effects logistic regression, and was found to systematically vary with spectral resolution. The use of formant cues was greatest for NH listeners for unprocessed speech, and declined in the two vocoded conditions. Compared to NH listeners, CI listeners relied less on formant transitions, and more on spectral tilt. Cue-weighting results showed moderately good correspondence with word recognition scores. The current approach to testing functional spectral resolution uses auditory cues that are known to be important for speech categorization, and can thus potentially serve as the basis upon which CI processing strategies and innovations are tested.

Neural Correlates of Phonetic Learning in Postlingually Deafened Cochlear Implant Listeners

“…However, it is possible that some CI users might be able to utilize a different acoustic cue in the naturally produced speech stimuli in the training sessions to categorize the speech contrasts, limiting the success of our training program for some listeners. Winn and Litovsky (2015) recently examined the perceptual weighting of the formant transition and spectral tilt cues used to categorize the /ba/-/da/ contrast in CI users. Their results suggest that, unlike NH listeners, CI users tend to weight the spectral tilt, the balance of high versus low frequency information, more heavily than the formant transition cue when categorizing /ba/ versus /da/.…”

Perceiving foreign-accented speech with decreased spectral resolution in single- and multiple-talker conditions

“…Although the difficulties experienced by CI users may be due to reduced spectral resolution, additional factors such as frequency-to-place mismatch, electrical channel interaction, and etiology of deafness also constrain speech intelligibility in CI recipients (Winn and Litovsky, 2015). These additional factors make it difficult to assess the contribution of spectral resolution alone.…”

Comparison of the Spectral-Temporally Modulated Ripple Test With the Arizona Biomedical Institute Sentence Test in Cochlear Implant Users

“…Measures of spectral resolution, such as the traditional spectral ripple test (Henry & Turner 2003) or spectral tilt measures (Winn & Litovsky 2015), which do not rely on such learned associations, offer a solution to this problem. In general, it has been shown that better spectral resolution correlates with better speech recognition in noise for CI users (Drennan et al 2016; Henry & Turner 2003; Holden et al 2016; Won et al 2007; however, see Langner et al 2017).…”