Effects of Nonlinear Frequency Compression on ACC Amplitude and Listener Performance
Year: 2015
Type: article
Abstract: In Brief Objectives: Nonlinear frequency compression is a signal processing technique used to increase the audibility of high-frequency speech sounds for hearing aid users with sloping, high-frequency hearing loss. However, excessive compression ratios may reduce spectral contrast between sounds and negatively impact speech perception. This is of particular concern in infants and young children who may not be able to provide feedback about frequency compression settings. This study explores the use of an objective cortical auditory evoked potential that is sensitive to changes in spectral contrast, the acoustic change complex (ACC), in the verification of frequency compression parameters. Design: ACC responses were recorded from adult listeners to a spectral ripple contrast stimulus that was processed using a range of frequency compression ratios (1:1, 1.5:1, 2:1, 3:1, and 4:1). Vowel identification, consonant identification, speech recognition in noise (QuickSIN), and behavioral ripple discrimination thresholds were also measured under identical frequency compression conditions. In Experiment 1, these tasks were completed in 10 adults with normal hearing. In Experiment 2, these same tasks were repeated in 10 adults with sloping, high-frequency hearing loss. Results: Repeated measures analysis of variance was completed for each task and each group with frequency compression ratio as the within-subjects factor. Increasing the compression ratio did not affect vowel identification for the normal hearing group but did cause a significant decrease in vowel identification for the hearing-impaired listeners. Increases in compression ratio were associated with significant decrements in ACC amplitudes, consonant identification scores, ripple discrimination thresholds, and speech perception in noise scores for both groups of listeners. Conclusions: The ACC response, like speech and nonspeech perceptual measures, is sensitive to frequency compression ratio. Additional study is needed to establish optimal stimulus and recording parameters for the clinical application of this measure in the verification of hearing aid frequency compression settings. Nonlinear frequency compression (NLFC) is a signal processing technique designed to improve the audibility of high-frequency speech sounds for hearing aid users. While NLFC can increase audibility, it may also cause perceptually disadvantageous spectral distortion. This study examines the sensitivity of the acoustic change complex (ACC) to nonlinear frequency compression ratio when elicited by a spectral ripple contrast stimulus. As hypothesized, ACC amplitude and speech perception in noise and quiet were found to decrease with increasing frequency compression ratio. These results indicate that the ACC may be a useful objective tool for evaluating NLFC settings in individual listeners.
Source: Ear and Hearing
Authors: Benjamin James Kirby, Carolyn J. Brown
Language: English
Subfield: Cognitive Neuroscience
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2394993344