BROAD-BAND ACOUSTIC TRANSMISSION INTENSITY FLUCTUATIONS IN THE TYRRHENIAN SEA

An acoustic propagation experiment was carried out in the Tyrrhenian S ea in October 1985 in which signals from a broadband source were recor ded at a range of 5 km with a vertical 62-m hydrophone array over a pe riod of 5 days. The experiment, named ''NAPOLI 85,'' was designed to i nvestigate the transfer function of the ocean medium over an acoustic frequency range from 250-2000 Hz as a function of time and position do wn the vertical array. This paper treats the ocean transfer function i n both the time and frequency domains for the lower refracted path. Th e intensity fluctuations down the array at an acoustic frequency of 1 kHz are presented for the 5 days. Large fluctuations occur simultaneou sly over the whole extent of the array, and these can be explained by refractive effects in an intrusive layer. There are also weak spatial variations down the array arising from diffractive effects in the laye r. The physical mechanisms causing the time variations in the layer ar e not yet understood. (C) 1996 Acoustical Society of America.