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

Abstract

Background Several studies have shown that hearing thresholds alone cannot adequately predict listeners' success with hearing-aid amplification. Furthermore, previous studies have shown marked differences in listeners' susceptibility to distortions introduced by certain nonlinear amplification parameters. Purpose The purpose of this study was to examine the role of spectral resolution, working memory, and audibility in explaining perceptual susceptibility to temporal envelope and other hearing-aid compression-induced distortions for listeners with mild to moderate and moderate to severe hearing loss. Research Design A between-subjects repeated-measures design was used to compare speech recognition scores with linear versus compression amplification, for listeners with mild to moderate and moderate to severe hearing loss. Study Sample The study included 15 adult listeners with mild to moderate hearing loss and 13 adults with moderate to severe hearing loss. Data Collection/Analysis Speech recognition scores were measured for vowel-consonant-vowel syllables processed with linear, moderate compression, and extreme compression amplification. Perceptual susceptibility to compression-induced temporal envelope distortion was defined as the difference in scores between linear and compression amplification. Both overall scores and consonant feature scores (i.e., place, manner, and voicing) were analyzed. Narrowband spectral resolution was measured using individual measures of auditory filter bandwidth at 2000 Hz. Working memory was measured using the reading span test. Signal audibility was quantified using the Aided Audibility Index. Multiple linear regression was used to determine the predictive role of spectral resolution, working memory, and audibility benefit on listeners' susceptibility to compression-induced distortions. Results For all listeners, spectral resolution, working memory, and audibility benefit were significant predictors of overall distortion scores. For listeners with moderate to severe hearing loss, spectral resolution and audibility benefit predicted distortion scores for consonant place and manner of articulation features, and audibility benefit predicted distortion scores for consonant voicing features. For listeners with mild to moderate hearing loss, the model did not predict distortion scores for overall or consonant feature scores. Conclusions The results from this study suggest that when audibility is adequately controlled, measures of spectral resolution may identify the listeners who are most susceptible to compression-induced distortions. Working memory appears to modulate the negative effect of these distortions for listeners with moderate to severe hearing loss.

Individual Sensitivity to Spectral and Temporal Cues in Listeners With Hearing Impairment

“…The idea that listeners with hearing loss will be forced to shift reliance to temporal cues has been put forth in several papers (Boothroyd, Springer, Smith, & Schulman, 1988; Christensen & Humes, 1997; Davies-Venn & Souza, 2014; Davies-Venn, Souza, Brennan, & Stecker, 2009; Souza, Jenstad, & Folino, 2005). That hypothesis relies, in part, on the idea that temporal cues will be more resistant to degradation from hearing loss than spectral cues, provided the listener can access a sufficiently wide signal bandwidth.…”

“…Without this distinction, a common rehabilitation approach might be to use fast-acting compression amplification to improve audibility of low-intensity phonemes. Because that type of amplification would also distort temporal envelope cues (Jenstad & Souza, 2005), it is possible that such a strategy may be detrimental to the listener who depends to a greater extent on temporal cues (Davies-Venn & Souza, 2014). Conversely, use of a high number of compression channels—which may improve audibility at the expense of smoothed frequency contrasts (Bor, Souza, & Wright, 2008)--may be detrimental to the listener who depends to a greater extent on spectral cues.…”

The Physiologic and Psychophysical Consequences of Severe-to-Profound Hearing Loss

“…This has been validated in correlational studies, in which spectral ripple has been shown to relate to other behavioral estimates of frequency selectivity including tone detection in notched noise and high-rate spectral modulation detection. 50,51 Spectral ripple is particularly suitable to assess frequency selectivity in listeners with cochlear implants and severe hearing impairment because the stimuli can be presented in a narrow dynamic range. All other measures of frequency selectivity require increasing the level of a signal until another signal that differs in frequency or time becomes inaudible, and the increase in level can approach the loudness discomfort level of a listener with a limited dynamic range.…”

“…[98][99][100] Some of those authors also have noted variability among individuals, such that some seem more sensitive to the effect than others. 98,101 Others have noted that the reduced benefit of amplitude compression is associated with phoneme confusions that depend on TE 51,102 and that the effect is reduced by using longer time constants which minimize envelope distortion. 103 Following from such findings, some commercial hearing aids now employ envelope-preserving processing for listeners with severe or profound loss.…”

Using Cognitive Screening Tests in Audiology

“…Recent research has suggested a relationship between cognitive ability and hearing aid setting in older users. With wide dynamic range compression, which is a common processing feature in most digital hearing aids, listeners with lower working memory capacity have more difficulty understanding speech processed by wide dynamic range compression with fast release time than with slow release time (Davies-Venn & Souza, 2014;Foo, Rudner, Rönnberg, & Lunner, 2007;Lunner & Sundewall-Thorén, 2007;Ohlenforst, Souza, & MacDonald, 2015;Souza & Sirow, 2014). Although cognitive ability, such as working memory capacity, is a significant factor for choosing individual release time setting, the time and resources needed to quantify cognitive ability are potential barriers for implementing cognitive tests in a clinical setting.…”