title: The depth-dependence of rain noise in the Philippine Sea.
abstract: 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.
authors: Marine Physical Laboratory, Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0238, USA.
authors: David R
authors: DR
authors: Barclay
authors: Michael J
authors: MJ
authors: Buckingham
mesh_terms: D000162:Acoustics / Q000295:instrumentation; D004867:Equipment Design; D009038:Motion; D009622:Noise; D009792:Oceans and Seas; D011891:Rain; D012815:Signal Processing, Computer-Assisted; D013016:Sound; D013018:Sound Spectrography; D014160:Transducers, Pressure; D014867:Water
chemical_list: D014867:Water