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

2pUW8. Mechanisms causing special features of ambient noise statistics in shallow water.

Jacob George

Naval Res. Lab., Code 7176, Stennis Space Center, MS 39529

Special features of ambient noise statistics, distinct from signal statistics, have been previously reported [J. Acoust. Soc. Am. 94, 1820(A) (1993)]. A possible mechanism for these features had been identified through simulation and from normal mode theory as depth fluctuations of a noise source close to the surface. Since then, the cumulative effect of multiple sources of this kind has been investigated following the techniques used by Dyer in analyzing distant shipping noise [J. Acoust. Soc. Am. 53, 564 (1973)]. The results show that while a single source assumption does fit experimental results, assumption of multiple sources does not. Because several merchant ships were known to be present during the data collection, it is unlikely that ambient noise was dominated by a single source. This suggests that additional mechanisms such as wind-generated noise may also be responsible for the observed features. The usefulness of the single source formula as an empirical fit to data, and as an important potential contributor to the observed statistical features will be discussed. [Work supported by ONR, with technical management provided by NRL/SSC.]