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sonic boom ocean penetration: noise metric comparison and initial focusing resultsThe purpose of the present research is to determine the impact by sonic boom noise penetration into the ocean. Since the 1994 LaRC High Speed Research Program Sonic Boom Workshop several new results have been obtained. This talk reviews these results, and emphasizes the two most important findings. The first major result is an improved understanding of the noise spectra of the penetrating sonic boom. It was determined that weighted sound exposure levels decrease with deeper ocean depths significantly faster than unweighted sound exposure levels. This is because low frequencies penetrate the ocean deeper than high frequencies. Several noise metrics were used including peak, SEL, C-SEL, A-SEL, and PLdB, and results are given for all. These results are important because they show that the sonic boom noise impact on marine life a few meters below the ocean surface may be significantly lower using weighted sound levels than if one were to measure the impact using unweighted levels. The other major finding is the first estimate of the worst case peak levels produced by a penetrating sonic boom being focused by a sinusoidal ocean surface. The method of analysis chosen was computational, a time domain finite difference algorithm. The method is outlined and then example results are presented. For rounded sonic boom waveforms incident on a sinusoidal ocean surface, it is shown that the percentage increase or decrease in pressure is only occasionally larger than 10%, rarely 25%. These fluctuations indicate, under the assumptions already given, that any increase or decrease in sound level underwater due to focusing or defocusing should be small, less than 3 dB.
Document ID
19960055066
Document Type
Conference Paper
Authors
Sparrow, Victor W.
(Pennsylvania State Univ. University Park, PA United States)
Date Acquired
August 17, 2013
Publication Date
July 1, 1996
Publication Information
Publication: The 1995 NASA High-Speed Research Program Sonic Boom Workshop
Volume: 1
Subject Category
Acoustics
Funding Number(s)
CONTRACT_GRANT: NAG1-1638
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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IDRelationTitle19960055049Analytic PrimaryThe 1995 NASA High-Speed Research Program Sonic Boom Workshop
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