Accession Number : AD0724349

Title :   Sound Propagation in Shadow Zones.

Descriptive Note : Technical rept.,

Corporate Author : CAMBRIDGE ACOUSTICAL ASSOCIATES INC MASS

Personal Author(s) : Sachs,David A.

Report Date : FEB 1971

Pagination or Media Count : 69

Abstract : Sound propagation in stratified media such as the ocean is conveniently analyzed using geometric (ray) acoustics. In this theory, sound energy propagates along curved trajectories, the rays. However, in regions behind certain curves called caustics, formed from envelopes of intersecting rays, no rays penetrate and ray theory predicts no sound disturbance whatever. Yet experimental observations indicate not only detectable but significant signals in these shadow zones. The author extends traditional ray theory into the shadow zone by admitting complex-valued solutions to the equations of ray acoustics. The theory is applicable to realistic sound speed profiles and encompasses both transient as well as harmonic sound sources. In the steady-state case, the sound field in the shadow is found to decay exponentially with frequency and with distance from the caustic. Within its approximations, the theory appears to be in agreement with experimental results. (Author)

Descriptors :   (*SOUND TRANSMISSION, INTERACTIONS), (*UNDERWATER SOUND, SOUND TRANSMISSION), INTENSITY, HARMONIC ANALYSIS, MATHEMATICAL ANALYSIS, UNDERWATER EXPLOSIONS

Subject Categories : Acoustics

Distribution Statement : APPROVED FOR PUBLIC RELEASE