Accession Number : ADA309158

Title :   Mechanisms of Bubble-Related Oceanic Ambien Noise.

Descriptive Note : Final rept. 1 Apr 90-14 Apr 93,

Corporate Author : JOHNS HOPKINS UNIV COCKEYSVILLE MD BALLISTIC ANALYSIS LAB

Personal Author(s) : Prosperetti, Andrea

PDF Url : ADA309158

Report Date : 14 APR 1993

Pagination or Media Count : 25

Abstract : The report contains a list of papers completed in the course of the project and a copy of the first page of each, which includes the abstract. The main achievements of the activity carried out under this grant have been an understanding of the mechanism of rain noise and of the role of bubble clouds in ambient noise generation at low frequencies. The first problem has been investigated theoretically in conjunction with experiments carried out at the University of Mississippi by Prof. Larry Crum and co-workers. In addition to reaching an understanding of a puzzling "universality" of rain noise at low rainfall rates, we have for the first time produced entirely numerical rain noise spectra resembling the observed ones. As a consequence of the publicity reached by this work, the PI was asked to provide a review paper on the problem for the Annual Reviews of Fluid Mechanics. Work on the second problem has been based on the initial observation of the PI (and, independently of Dr. W. Carey), originally formulated in a paper presented in 1985 at the Nashville meeting of the Acoustical Society of America, that bubble clouds could oscillate in collective modes at frequencies as low as a few tens of Hz, even though the constituent bubbles, in isolation, might have natural frequencies of tens of kHz or more. This hypothesis has now been widely confirmed both in the laboratory and in the field and constitutes the accepted answer to a puzzle that had remained unsolved since the original measurements of Knudsen during World War II. The results of the work are documented in a series of listed papers. The first page of each paper is shown. Additional information on the work carried out under this grant is provided in the annual summaries submitted to ONR and published in part in the series of annual volumes titled Ocean Acoustics Program Summary.

Descriptors :   *BUBBLES, *UNDERWATER ACOUSTICS, CLOUDS, OCEAN WAVES, IMPACT, RESONANT FREQUENCY, RAINFALL INTENSITY, RAINDROPS, DROPS, ATMOSPHERIC PRECIPITATION, ACOUSTIC SCATTERING, AMBIENT NOISE, FLUID MECHANICS.

Subject Categories : Acoustics
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE