1pAO5. Shallow-water ambient noise caused by breaking waves in the surf zone.

Session: Monday Afternoon & Evening, May 13

Time: 2:25

Author: Oscar B. Wilson
Author: Marc S. Stewart
Location: Naval Postgrad. School, Dept. of Phys., Monterey, CA 93943
Author: James H. Wilson
Location: Neptune Sciences, Inc., San Clemente, CA 92674
Author: Robert H. Bourke
Location: Naval Postgrad. School, Monterey, CA 93943


Ambient noise measurements made by Wilson, Wolf, and Ingenito in Monterey Bay, California in 1980 and 1981 were combined with modeled transmission loss (TL) to estimate the spectral source level of surf-generated noise. In the frequency range 20--700 Hz the horizontal directionality of these noise data showed much higher levels from shore than seaward and the overall noise levels decreased with range from shore, strongly suggesting that surf noise was a significant contributor. A Hamilton geoacoustic model of the coastal environment has been derived and used in a finite element parabolic equation propagation loss model to obtain the TL values. These indicate that propagation is significantly dependent on the environment and frequency, particularly near the surf zone. Estimates of wind and local wave noise intensity corrected for the local environment were subtracted from the total measured noise field to determine the contribution due to surf only. Heavy surf breaking on a uniform 12.5-km linear section of beach near Fort Ord was found to be the dominant source of surf-generated noise. The preliminary results provide estimates of the noise source level densities for heavy and light surf at Fort Ord beach. [sup a)]Currently at Naval Sea Systems Command, Arlington, VA 22242-5160.

from ASA 131st Meeting, Indianapolis, May 1996