Experimental analysis on air-to-water sound transmission loss in shallow water

Research on the propagation characteristics of air-to-water sound transmission is of great importance to the detection of aerial target from underwater. In order to study the propagation characteristics of air-to-water sound transmission in shallow water, an experiment was conducted in the South China Sea in March, 2013. During the experiment, signals transmitted by a hooter hung on a research ship were received by an underwater hydrophone. The source signals were also recorded by a microphone under the hooter. The distance between the hooter and the hydrophone was from 2.4 km to 9.8 km approximately. Data measured during the experiment is analysed in this paper. The transmitted signals and received signals were carefully filtered and calibrated one-by-one. It is shown that the SNRs at 9.8km are up to 12 dB and 18 dB at the frequencies 128 Hz and 256 Hz, respectively. The experimental air-to-water sound transmission loss is estimated up to 9.8 km in range, which has clear oscillation structure. A wave-number integration approach is used to predict the air-to-water transmission losses, which are in good agreement with experimental data