Underwater noise caused by precipitation

Abstract

The characteristics of underwater noise in the ocean generated by precipitation are important to weather forecasters and oceanographers since they permit the detection and measurement of rain over the ocean by remote (i.e., buoyed or bottom-mounted) acoustic sensors. We have recently observed the character of the underwater noise generated by rain, hail, and snow. The spectrum of rain noise, for wind speeds below 1.5 m/s, shows a peak of 13.5 kHz with a sharp cutoff on the low-frequency side and a gradual falloff (7 dB per octave) on the high-frequency side. Stronger winds smear the peak. Hail spectra show a peak at 3.0 kHz with a gradual (roughly 11 dB per octave) falloff on both sides. The spectrum of snow noise is unique. Our instrumentation permitted the measurement of the drop (or stone) size distributions in the precipitation. These findings will enhance the art of remote acoustic sensing in oceanograpy. [Work supported by: Supply & Services Canada; Institute of Ocean Sciences, Sidney, BC, Canada; Atmospheric Environment Service, Toronto, Canada; and Department of National Defence, Canada.]

Bubble entrainment by the impact of drops on liquid surfaces

“…Hence if, as experiment suggests (Pumphrey & Crum 1988;Pumphrey et al 1989), only bubble-entrapping drops contribute to the underwater noise of rain, one would expect this noise to exhibit a peak a t a rather well-defined frequency, corresponding to the natural frequency of the entrained bubbles. This is precisely what is observed experimentally (Scrimger 1985;Scrimger et al 1987 ;Scrimger, Evans & Lee 1989;Prosperetti et al 1989), with the peak around 14-15 kHz. While we shall present detailed calculations lending further support to this hypothesis in a separate publication, we remark here that our computations estimate the radii of the bubbles entrained by drops to be between 0.19 and 0.30 mm.…”

The Impact of Drops on Liquid Surfaces and the Underwater Noise of Rain

“…Publication of this result was however delayed until 1986. In 1984 Scrimger and coworkers (who had been in contact with both Nystuen and Farmer) made similar measurements in Canada with analogous results and were 582 PROSPERETTI & O~;UZ the first to report the discovery in the open literature (Scrimger 1985;Scrimger et al 1987Scrimger et al , 1989. The remarkable results obtained by these investigators can be illustrated with reference to Figure 3 (from Scrimger et al 1987).…”

Receiving Distance of the Stationary Ultrasonic Biotelemetry Receiver in the Temperate Ocean

“…This is conjectured to be because for pistol shrimp to inhabit this ocean space widely. This noise is mainly the frying noise by pistol shrimp [13] [14]. Until now, there was no example that quantified the influence on this frequency.…”