Bistatic volume propagation measurements at the Azores Fixed Acoustic Range

Abstract

The time, frequency, and angular spreads imposed on acoustic transmissions by inhomogeneities in the ocean volume have been measured over 1.5- and 18-mile purely refracted paths. The dependence of these spreads on acoustic frequency has been investigated and results over the range of frequencies from 400 to 5000 Hz are presented. Fluctuations in received intensity have also been quantified and results are presented in the form of log variance as a function of range and frequency. The transition from the weak to strong (saturated) regime is clearly visible as range and frequency are increased. The large quantity of available data, the long averaging times used, and the consistency of results over many experiments, together with the availability of detailed simultaneous measurements of oceanographic parameters, make the results especially valuable in the evaluation of acoustic propagation models. [Work supported by NAVSEA, ONR, and ARPA.]

The intensity coherence function of time for partially saturated acoustic propagation through ocean internal waves

“…18,19 We focus specifically on the 35-km transmission centered at 1010 Hz, which is found to be in the partially saturated regime. Reynolds et al also found the statistics of the sound field to be nominally fit by the GarrettMunk internal-wave formulation with the following parameter values: n 0 Bϭ3.0 cph-km, 0 ϭ13.1 m, and j * ϭ3, and determined the fluctuation parameters, using the definitions given in Flatté et al, 1 as ⌳⌽ 2 ϭ3.0 and ⌳⌽ϭ0.…”