Accession Number : AD0672914

Title :   FOCUSING OF SOUND AND EXPLOSIVE PULSES IN THE OCEAN.

Descriptive Note : Technical rept.,

Corporate Author : CAMBRIDGE ACOUSTICAL ASSOCIATES INC MASS

Personal Author(s) : Silbiger,Alexander

Report Date : JUN 1968

Pagination or Media Count : 42

Abstract : Pressure disturbances propagating in the ocean may converge as a result of gradients in the sound velocity. Significant amplifications above the levels predicted by spherical spreading have been observed for continuous waves as well as for explosive pulses. Published theories concerning convergence zones generally have only dealt with time-harmonic waves and idealized sound velocity profiles. A comprehensive theory is presented here, applicable to realistic profiles and encompassing transient as well as harmonic pulses. For waves originating at a point source it is shown that at most one caustic is encountered after the traversal of a turning point. The pulse spectrum amplification exhibits a marked frequency dependence, as a result of which the pulse shape undergoes considerable distortion, with enhancement of the high frequency components. After passing through the caustic region the pulse regains the original power spectrum; its shape will however remain distorted as the result of a phase shift. The analysis is restricted to the early time behavior (near the shockfront) and does not include large amplitude and viscous effects. Within these limitations the conclusions appear to be in agreement with experimental results. (Author)

Descriptors :   (*UNDERWATER EXPLOSIONS, *SOUND TRANSMISSION), (*UNDERWATER SOUND, FOCUSING), SHOCK WAVES, HARMONIC ANALYSIS, FREQUENCY, DISTORTION, PHASE SHIFT CIRCUITS, REFRACTION, BOUNDARY LAYER, BOUNDARY VALUE PROBLEMS

Subject Categories : Explosions
      Acoustics

Distribution Statement : APPROVED FOR PUBLIC RELEASE