Sound focusing and scanning in shallow water with background internal wave field

Abstract

Sound field focusing and scanning with focal spot are investigated for shallow water and long distances (up to 30km). It is studied the availability of horizontal and vertical scanning for controlling long‐range low‐frequency bottom reverberation as well. These researches are carried out by using numerical modeling for typical acoustic waveguides including random ones with background internal waves. The acoustic field is focused with vertical array by phase conjugation of sound wave from probe source placed at preset point. Horizontal scanning with the focal spot is performed by radiation frequency tuning. It is demonstrated that the best feasibility for scanning and hence for controlling bottom reverberation takes place for the regular waveguide under winter conditions when sound speed depends on depth only slightly and background internal waves are nonexistent practically. As an example for these conditions we can control the bottom reverberation on interval ̃ 5km in the neighborhood of preset point. In summer for near bottom sound waveguide the range of distances for which it is practicable is much narrower even without internal waves. For the waveguide with intense background internal waves the control of long‐range bottom reverberation becomes impossible. The work was supported by RFBR Project 05‐02‐16842.