ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

2pPP41. Temporal symmetry in auditory perception and the auditory system.

Toshio Irino

NTT Basic Research Lab., 3-1, Morinosato Wakamiya, Atsugi-shi, Kanagawa, 243-01, Japan

Roy D. Patterson

MRC Applied Psychology Unit, Cambridge CB2 2EF, UK

When a repeating damped exponential is used to modulate a sinusoid or noise, the carrier component of the perception is suppressed. When these ``damped'' sounds are reversed in time, producing ``ramped'' sounds, the carrier is restored. [R. D. Patterson, 1419--1428 (1994); M. A. Akeroyd and R. D. Patterson, 2941(A) (1994)]. We report matching experiments designed to measure the perceptual asymmetry between damped and ramped sounds directly. Listeners compared the relative strengths of the transient and continuous components in pairs of damped and ramped sounds, and the damped half life was varied to produce a match in the relative strengths of the transient and continuous components of the two sounds. For sinusoidal and noise carriers, the half life of the damped sound has to be, respectively, 5 and 2.5 times that of the corresponding ramped sound to produce the match. A ``delta-gamma'' theory of intensity enhancement around acoustic transients [T. Irino and R. D. Patterson, 2943(A) (1994)] is used to explain the perceptual asymmetry. The theory is also used to compare the asymmetry produced by different auditory models.