ASA 127th Meeting M.I.T. 1994 June 6-10

1pUW5. A theoretical model of bubble clouds as sources of noise in shallow water environment.

Hasan N. Oguz

Dept. of Mech. Eng., Johns Hopkins Univ., Baltimore, MD 21218

Wave breaking that leads to bubble cloud formation is known to be a major contributor to the underwater noise levels in the low-frequency range (100 Hz--1 kHz). The emission theory that was developed by the author [Oguz, J. Acoust. Soc. Am. (to be published)] for deep ocean has been extended to handle shallow water environments. The model consists of a bubble cloud system excited by the injection of bubbles during a wave breaking event. The bottom effects are incorporated by the method of images. For simplicity, only the soft and hard bottom cases are considered in this development. The resonance characteristics of the bubble cloud are not affected by the presence of a bottom for depths much larger than the cloud size. However, the far-field acoustic pressure of an individual bubble cloud differs considerably from the deep water case due to the interference between the source and its images. As a result, the ambient noise level distribution in shallow water can be markedly different than in deep ocean. The results are compared with field measurements and a good agreement is found. [Work supported by the ONR.]