Consequences of Broad Auditory Filters for Identification of Multichannel-Compressed Vowels

Abstract

Purpose In view of previous findings (Bor, Souza & Wright, 2008) that some listeners are more susceptible to spectral changes from multichannel compression (MCC) than others, this study addressed the extent to which differences in effects of MCC were related to differences in auditory filter width. Method Listeners were recruited in three groups: listeners with flat sensorineural loss, listeners with sloping sensorineural loss, and a control group of listeners with normal hearing. Individual auditory filter measurements were obtained at 500 and 2000 Hz. The filter widths were related to identification of vowels processed with 16-channel MCC and with a control (linear) condition. Results Listeners with flat loss had broader filters at 500 Hz but not at 2000 Hz, compared to listeners with sloping loss. Vowel identification was poorer for MCC compared to linear amplification. Listeners with flat loss made more errors than listeners with sloping loss, and there was a significant relationship between filter width and the effects of MCC. Conclusions Broadened auditory filters can reduce the ability to process amplitude-compressed vowel spectra. This suggests that individual frequency selectivity is one factor which influences benefit of MCC, when a high number of compression channels are used.

Effects of WDRC Release Time and Number of Channels on Output SNR and Speech Recognition

“…For example, while short RT may have been relatively more beneficial for some listeners due to the rapid increase in gain for low-intensity parts of speech, it may have been relatively more disadvantageous for others by increasing the noise floor ( i.e ., ambient noise in the recorded signal in this study or ambient room noise combined with microphone noise in the real world), thereby reducing the salience of information conveyed by temporal envelope in the presence of the masker (Plomp, 1988; Drullman et al ., 1994; Souza & Turner, 1998; Stone & Moore, 2003; 2007; Jenstad & Souza, 2005, 2007; Souza & Gallun, 2010). Similarly, while use of multiple channels may have relatively more beneficial for some listeners because gain for low-intensity speech could be rapidly increased in frequency-specific regions when and where it was needed the most (e.g., Yund & Buckles, 1995a; Henning & Bentler, 2008), it may have been relatively more disadvantageous for others because the increased gain for low-intensity frequency regions may have reduced the salience of information conveyed by spectral shape, including formant peaks and spectral tilt (Yund & Buckles, 1995b; Franck et al ., 1999; Bor et al ., 2008; Souza et al ., 2012). Furthermore, if the low-intensity temporal and spectral segments consisted primarily of noise, increased masking may have resulted (Plomp, 1988; Edwards, 2004).…”

“…Listeners with SNHL tend to have more difficulty processing changes in spectral shape and maintaining an internal representation of spectral peak-to-valley contrasts (e.g., Bacon & Brandt, 1982; Van Tassel et al ., 1987; Leek et al ., 1987; Turner et al ., 1987; Summers & Leek, 1994; Henry & Turner, 2003). An additional reduction in spectral contrast from multichannel WDRC can diminish the perception of speech sounds whose phonemic cues are primarily conveyed by spectral shape, for example, vowels, semivowels, nasals, and place of articulation for consonants (Yund & Buckles, 1995b; Franck et al ., 1999; Bor et al ., 2008; Souza et al ., 2012). Thus, performance for WDRC with short RTs, which also degrades temporal envelope cues, might decrease once the number of channels is increased beyond the point at which additional channels no longer optimize audibility (Stone & Moore, 2008).…”

The Role of Spectral Resolution, Working Memory, and Audibility in Explaining Variance in Susceptibility to Temporal Envelope Distortion

“…Souza et al (2012b) evaluated the effect of temporal envelope distortion on consonant features using spectrally degraded vowel-consonant-vowel (vCv) nonsense syllable tokens presented to listeners with normal hearing. They reported that under spectrally degraded conditions, listeners' scores decreased with increases in envelope distortion.…”

Application of the Envelope Difference Index to Spectrally Sparse Speech

“…Listeners might have been able to shift their attention to alternative cues to offset the impact of envelope distortions. With hearing loss which results in broader auditory filters, spectral cues may be less available (Tyler, Hall, Glasberg, Moore, & Patterson, 1984; Souza, Wright, Bor, submitted), and the importance of the envelope may be increased (Boothroyd, Springer, Smith & Schulman, 1988; Davies-Venn, 2010). Spectral cues will be even more limited for cochlear implant wearers, who typically receive only four to eight channels of spectral information (Friesen, Shannon, Baskent & Wang, 2001).…”