Further Studies of the Underwater Noise Produced by Rainfall
Abstract
A study of the sound produced by water drops striking a water surface has confirmed some earlier results. In particular, for a well defined range of impact velocities, drops will predictably and repeatedly entrain bubbles; this phenomenon has been named regular entrainment. In this present study, various drop diameters have been used to investigate how bubble frequency, dipole strength, and time between drop impact and bubble formation vary with impact velocity. It is found that as impact velocity is increased through the point where entrainment begins, both frequency and dipole strength decrease to a minimum value and then rise again as the highest velocity at which entrainment occurs is approached. Both terms show increased variability near the critical upper and lower velocities. The frequency tends to increase monotonically as drop size is reduced; drops that entrain bubbles at their terminal velocities tend to produce frequencies near 14 kHz, which is also the peak frequency of the natural rainfall spectrum. Finally, the time between drop impact and bubble formation was found to increase monotonically as drop size or impact velocity increases. Keywords: Underwater noise; Ambient noise. (JHD)
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 17, 1989
- Accession Number
- ADA213010
Entities
People
- Hugh C. Pumphrey
- Lawrence A. Crum
- Paul A Elmore