During the Philippine Sea experiment in May 2009, Deep Sound, a free-falling instrument platform, descended to a depth of 5.1 km and then returned to the surface. Two vertically aligned hydrophones monitored the ambient noise continuously throughout the descent and ascent. A heavy rainstorm passed over the area during the deployment, the noise from which was recorded over a frequency band from 5 Hz to 40 kHz. Eight kilometers from the deployment site, a rain gauge on board the R/V Kilo Moana provided estimates of the rainfall rate. The power spectral density of the rain noise shows two peaks around 5 and 30 kHz, elevated by as much as 20 dB above the background level, even at depths as great as 5 km. Periods of high noise intensity in the acoustic data correlate well with the rainfall rates recovered from the rain gauge. The vertical coherence function of the rain noise has well-defined zeros between 1 and 20 kHz, which are characteristic of a localized source on the sea surface. A curve-fitting procedure yields the vertical directional density function of the noise, which is sharply peaked, accurately tracking the storm as it passed over the sensor station.
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May 06 2013
The depth-dependence of rain noise in the Philippine Sea
David R. Barclay;
David R. Barclay, Michael J. Buckingham; The depth-dependence of rain noise in the Philippine Sea. J. Acoust. Soc. Am. 1 May 2013; 133 (5): 2576–2585. https://doi.org/10.1121/1.4799341
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