Chemical absorption of acoustic energy due to an eddy in the western Bay of Bengal

Abstract

Acoustic energy losses due to chemical absorption, within the western Bay of Bengal, in the presence of a subsurface meso-scale cold core eddy has been analysed. These estimates, for two different frequencies - 400 Hz and 10 kHz, find applications in acoustic tomographic studies and SONAR operations. The results show that the eddy has been found to contribute to increased loss of acoustic energy due to chemical absorption. At 400 Hz the energy loss increases by 1.76 x 10@u-3@@ dB/km as against 1.0 x 10@u-1@@ dB/km for 10 kHz over the ambient value. The study also brings out the fact that the loss of acoustic energy due to chemical absorption even in the presence of a meso-scale eddy works out to a negligible percent (0.4) as compared to geometrical spreading for long ranges and at 400 Hz. For SONAR frequencies this loss amounts to 25%. Thus, in terms of range, the meso-scale features would limit the performance of SONAR