Measurements of acoustic ambient noise in shallow water due to breaking surf
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Authors
Wilson, O. B. (Oscar Bryan)
Wolf, Stephen N.
Ingenito, Frank
Subjects
Acoustic
Ambient noise
Monterey Bay
Shallow water
Surf
Ambient noise
Monterey Bay
Shallow water
Surf
Advisors
Date of Issue
1982-12
Date
1982-12
Publisher
Monterey, CA; Naval Postgraduate School
Language
en_US
Abstract
Horizontal directionality of ambient noise was measured at ranges up to 15 km from the south-eastern shore of Monterey Bay, California. Water depths at the sites ranged from 8 to 175 m. A steerable cardioid receiving pattern was formed using signals telemetered from dipole and omnidirectional hydrophones suspended from tethered buoys. With no nearby shipping, whenever the maximum of the cardioid pattern was directed toward the beach, noise levels in the frequency range from 20 Hz to 70 Hz were greater than those obtained when the maximum was directed seaward. This difference or anisotropy (seaward vs. shoreward), which depends on range from the beach, on frequency and on surf intensity, was 10 dB at 300 Hz at the 9 km site during very heavy surf. Surf beat was clearly audible when the cardioid maximum was steered shoreward at ranges as great as 2 km. During heavy surf, the omnidirectional ambient noise levels also increased significantly in the same frequency range at which the anisotropy is evident. The anisotropy effects diminish both in magnitude and in frequency range with lower wave height but are still observable during light surf. We have concluded that intense breaking surf can contribute significantly to ambient noise in fairly deep continental shelf waters. (Author)
Type
Technical Report
Description
Series/Report No
Department
Organization
Naval Postgraduate School (U.S.)
Identifiers
NPS Report Number
NPS-61-83-006
Sponsors
Prepared for: Chief of Naval Research, Arlington, VA 22237
Funder
N0001482WR20043
Format
30 p. ; 28 cm.
Citation
Distribution Statement
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.