Ambient noise level on vertical array in ASIAEX South China Sea experiment

Abstract

Previous literatures show that ambient noise in deep water should decrease with depth, but would it be the same in the shallow? The ASIAEX 2001 South China Sea experiment is on the continental shelf-break, with water depth from 100 m to 400 m, so the depth effect of ambient noise in shallow water can be explored. In this study, acoustic signal of ambient noise was collected on vertical line array, which has 16 elements, from 700 to 1200 Hz. From the results of this study, ambient noise has insignificant change with depth, however it is much affected by the variation of temperature, frequency, and occurrence of internal wave. Higher frequency tends to have lower SPL and the decay is of 5 dB/octave approximately. The temperature profile controls the vertical distribution of ambient noise level, so the internal wave effect can be significant. Moreover, the serious weather condition, like the typhoon during the experiment, can greatly increase the ambient noise level and change its distribution.