Localization of brief sounds: effects of level and background noise.
Listeners show systematic errors in vertical-plane localization of wide-band sounds when tested with brief-duration stimuli at high intensities, but long-duration sounds at any comfortable level do not produce such errors. Improvements in high-level sound localization associated with increased stimulus duration might result from temporal integration or from adaptation that might allow reliable processing of later portions of the stimulus. Free-field localization judgments were obtained for clicks and for 3- and 100-ms noise bursts presented at sensation levels from 30 to 55 dB. For the brief (clicks and 3-ms) stimuli, listeners showed compression of elevation judgments and increased rates and unusual patterns of front/back confusion at sensation levels higher than 40-45 dB. At lower sensation levels, brief sounds were localized accurately. The localization task was repeated using 3-ms noise burst targets in a background of spatially diffuse, wide-band noise intended to pre-adapt the system prior to the target onset. For high-level targets, the addition of background noise afforded mild release from the elevation compression effect. Finally, a train of identical, high-level, 3-ms bursts was found to be localized more accurately than a single burst. These results support the adaptation hypothesis.
Macpherson
E A
EA
Kresge Hearing Research Institute, University of Michigan, Ann Arbor 48109-0506, USA. emacpher@umich.edu
Middlebrooks
J C
JC
D000293:Adolescent; D000328:Adult; D001288:Attention; D005260:Female; D006801:Humans; D008144:Loudness Perception; D008297:Male; D009622:Noise; D011571:Psychoacoustics; D013017:Sound Localization; D013018:Sound Spectrography