SPECTRAL AND TEMPORAL WEIGHTING OF SOUND LOCALIZATION: EFFECTS OF COMPETING NOISE AND HEARING IMPAIRMENT

Abstract

A listener’s ability to localize sound primarily relies on the binaural cues available across frequency and time. Observer weighting methods have established the relative influence (or perceptual weighting) of these cues for horizontal plane localization and lateralization. Previous literature demonstrates that, across frequency, listeners rely on cues within an “ITD dominance region” near 400 to 1000 Hz with a peak near 800 Hz. Across time, listeners rely on cues at the onset portion of the stimulus, especially in reverberant environments. However, extant literature focused almost exclusively on quiet situations and listeners with normal hearing. How listeners perceptually weigh these cues for degraded signals due to a competing sound or the impairment of the auditory system has yet to be established. This study measured spectral and temporal perceptual weighting of degraded signals during localization. In the first two experiments, competing sounds were presented at lateral angles. The ITD dominance region peak broadened towards 400 Hz, and onset dominance was reduced. The second two experiments simulated hearing loss in normal-hearing listeners by implementing a diffuse masker. Weighting patterns were compared to those of participants with real sensorineural hearing loss. The ITD dominance region peak broadened towards 400 Hz for both participants with real and simulated hearing loss. Onset dominance was reduced for participants with simulated hearing loss. However, onset dominance remained prevalent in participants with real hearing loss. The now established weighting patterns reveal the spectrotemporal portions of stimuli utilized during localization when signals are degraded due to competing noise and hearing impairment.