Speech Understanding in Noise: An Auditory Event-Related Potentials Study
Fitzharris, Katharine Lynn
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The most common complaint of individuals with hearing loss is their inability to understand speech in noisy environments; thus, speech-in-noise (SIN) has been an area of tremendous research. It has been established that a complex interaction of peripheral and central auditory systems underlies the ability to comprehend speech in degraded environments. Methodologically, however, behavioral and electrophysiological studies have been disparate: where behavioral and clinical testing establishes a variable signal-to-noise ratio (SNR) threshold based on an individual’s performance, studies utilizing auditory event-related potentials (AERPs) tend to use fixed SNR values, resulting in variable performance. Both behavioral and AERP studies have illustrated the impact of stimulus effects on SIN performance, e.g., SNR and masker type. The purpose of this study was to use AERPs in order to evaluate the interactions between peripheral and central systems in the processing of speech. Using behaviorally-established SNR levels (60% correct, 100% correct), two types of background noise (speech-shaped noise, multitalker babble), and two signal types (syllables, words) in an oddball task, AERPs were recorded and analyzed relative to the peak amplitudes and latencies of the N1, P2, and P3. Results from 21 young adults indicate that even when behavioral accuracy is controlled for, there are complex effects of stimulus factors on the neural underpinnings of speech processing.