Amplification: Spectral Resolution, Working Memory, Audibility, and More
Davies-Venn and Souza (2014) report hearing thresholds (in isolation) do not provide enough information to predict an individual’s success with amplification. Spectral resolution, audibility, and working memory appear to be significant factors, too. Previous studies have shown individual differences in susceptibility to distortions secondary to non-linear amplification are likely to impact outcomes. Although a multitude of previous publications have shown compression systems are superior to linear systems when the compression system provides substantial improvements in audibility. Davie-Venn and Souza suggest compression benefits associated with audibility are beneficial and indeed, modulate “the distortive effect of flattening the temporal envelope of speech….”
The authors hypothesized listeners with poor spectral resolution would depend more on temporal resolution and would therefore, be susceptible to temporal envelope distortions. The authors evaluated 15 adults with mild-to-moderate sensorineural hearing loss (SNHL) and 13 adults with moderate-to-severe SNHL with respect to speech recognition scores using linear versus compression systems.
Davies-Venn and Souza report “overall speech recognition scores decreased for moderate and extreme compression compared with linear amplification for both listener groups….” These results were apparent for both groups (mild-to-moderate and moderate-to-severe). Additionally, speech recognition scores for the linear condition were significantly higher than the moderate and extreme compression condition. They report, “In this study, all listeners performed worse with compression compared with linear amplification.” As might be expected, listeners with moderate-to-severe SNHL had significantly poorer spectral resolution than did people with mild-to-moderate SNHL. For the moderate-to-severe SNHL group “spectral resolution was a significant predictor of susceptibility to temporal envelope distortion…” and their results suggest listeners with “poor spectral resolution were more dependent on temporal envelope cues and distorting these cues was more detrimental for them.
Davies-Venn and Souza indicate their findings support “a conscientious effort to improve audibility while minimizing distortion as the first priority of rehabilitation for listeners with hearing loss…” and “working memory appears to modulate the negative effect of these distortions for listeners with moderate to severe hearing loss.”
For More Information, References and Recommendations
Davies-Venn E, Souza P. (2014) The Role of Spectral Resolution, Working memory, and Audibility in Explaining Variance in Susceptibility to Temporal Envelope Distortion. Journal of the American Academy of Audiology. 25:592-604.