Frequency-dependent anamolies of sound propagation in the SWARM-95 experiment

Abstract

Frequency-dependent acoustic propagation is a subject of great interest in shallow-water regions. The phenomenon known as resonance absorption occurs when broadband sound signals propagate across the crests of internal solitary waves (ISWs) if the sound field satisfies the condition of space synchronization. In this paper we show that different anomalies in frequency dependence can take place when sound signals propagate along the wave fronts of ISWs. These anomalies result from the anisotropic properties of the ISWs that can produce frequency-dependent horizontal refraction of acoustic waves in the ocean. Sound propagation of broadband pulses in the SWARM-95 experiment is analyzed from this point of view. The nature of such behavior is connected with the selective (over modes and frequencies) character of thermocline perturbations caused by ISWs. [Work supported by ONR and US CRDF Award No. VZ-010-00.]