ASA 125th Meeting Ottawa 1993 May

5aUW8. Ambient noise measurements in the southern Norwegian Sea.

S. F. Kooney

Naval Res. Lab., Stennis Space Center, MS 39529-5004

Ambient noise horizontal directionality measurements were made in the southern Norwegian Sea by a towed horizontal line array during March 1992. The measurements were taken at three sites near an oceanographic front. The first site was north of the front, the second site was within the front, and the last site was south of the front. The ambient noise results, omnidirectional levels, and various beam noise statistics are discussed. In general, the low-frequency ambient noise showed approximately 15 dB more noise coming within a broad sector to the east and decreased with increased frequency. Along other azimuths, high levels in the horizontal directionality patterns correlated well with directions in which the bathymetry provided windows for the noise to propagate to the site from distant ships. The beam noise statistics at all three sites showed that the ambient noise possessed a high degree of spatial anisotropy at frequencies below 150 Hz and very little at frequencies of 300 Hz and above. [Work sponsored by the Office of Naval Research.]