Sea-surface wind speed has significant impacts on ocean ambient noise at medium and low frequency bands. When a typhoon comes close, sea-surface wind speed increases sharply, which results in the surge of the ambient noise level. By analyzing the sound data collected by a vertical array in deep ocean environment during two typhoon periods, both the wind speed and frequency dependencies of ambient noise are established. Noise field at receivers is calculated via numerical simulations with combination of the source intensity model of wind generated noise and the typhoon generated noise intensity model. Simulated noise intensity is fitted with the experimental data by least square method, through which the exponent of the wind speed and frequency in the source intensity model is determined. Our result indicate that the variations of wind speed caused by typhoon heavily impact on the noise at frequency band higher than 200 Hz. And specifically, the ambient noise intensity is approximately proportional to the 34 power of the wind speed, where the exponent of frequency is around -0.85.
SCIENTIA SINICA Physica,Mechanica ＆ Astronomica
typhoon, ocean ambient noise, wind speed, frequency