Identification and discrimination of azimuth with passive and active hearing protectors

Abstract

Three studies are reported in which auditory localization ability is measured with and without hearing protectors. Assessment is made under two methods. Identification is indication on an analog of perceived azimuth of the stimulus. Identification data are presented as response frequency surfaces for 36 stimulus azimuths at 10° intervals. Discrimination measures were made under a two-alternative forced-choice matching paradigm for temporally and spatially disparate stimuli. Data are presented as psychometric functions of proportions of correct responding. Results of these studies indicate that passive circumaural devices degrade localization ability by eliminating pinna cues and by modifying spectral cues. Active devices tested severely disrupted localization and produced sometimes bizarre patterns of responding by eliminating interaural difference cues or by severely distorting signals. Stimuli were long duration broadband noise bursts.