Effects of Amplitude Compression on Relative Auditory Distance Perception

Report No. ARL-RP-464
Authors: Ashley Foots
Date/Pages: October 2013; 66 pages
Abstract: Military C&HPS use amplitude compression to provide protection and prevent distortion which has the potential to affect relative auditory distance perception by reducing the level differences between sounds. The focus of the present study was to investigate the effect of amplitude compression on relative auditory distance perception.

Impulse responses were recorded through KEMAR and convolved with pink noise and a dog bark to create stimuli. Two levels of amplitude compression were applied to the recordings through Adobe Audition sound editing software to simulate military C&HPS.

Data were collected in 12 conditions based on combinations of three independent variables: reference distance (6.5 ft, 16.5 ft), stimulus (pink noise, dog bark) and compression (none (linear), low, high). Participants listened to the stimuli through insert earphones in a 2IFC adaptive task and selected the stimulus they perceived to be farther away. As the participant selected the correct stimulus, the computer program reduced the separation in the next trial. The dependent variable was the smallest average separation in distance across 3-5 runs.

A 3-factor Analysis of Variance showed significant main effects of distance and compression as well as significant interactions between the three variables. Follow-up analyses within each stimulus indicated that the effects of compression varied between v the two stimuli. For both stimuli, listeners needed increased separation as the compression level increased. For the pink noise, the effect of compression was greater for the 6.5 ft distance than the 16.5 ft distance. For the dog bark stimulus, the low level of compression affected perception greater at the 6.5 ft distance than at the 16.5 ft distance.
Distribution: Approved for public release
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Last Update / Reviewed: October 1, 2013