2pUW11. Acoustic intensity fluctuations induced by internal waves in a shallow-water waveguide.

Session: Tuesday Afternoon, December 3

Time: 4:20

Author: Steven Finette
Location: Acoust. Div., Naval Res. Lab., Washington, DC 20375
Author: Altan Turgut
Location: Acoust. Div., Naval Res. Lab., Washington, DC 20375
Author: John Apel
Location: Global Ocean Assoc., Silver Spring, MD 20908


The SWARM (Shallow Water Acoustics in a Random Medium) experiment performed during July--August 1995 made simultaneous acoustic and oceanographic measurements along a 45-km track on the continental shelf off the New Jersey coast. The area is a site of intense internal wave activity, primarily in the form of soliton packets that perturb the sound-speed profile in range, depth, and time. Incorporating environmental parameters estimated from SWARM measurements, computer simulation results are presented for acoustic propagation through this environment at frequencies of 224 and 400 Hz. A wide-angle parabolic equation method was used to compute multiple realizations of the acoustic field. The simulations employed bathymetry and sub-bottom acoustic parameters estimated from chirp sonar surveys. Oceanographic parameters were obtained from thermistor strings and yo-yo CTDs in conjunction with satellite images, which allowed for estimation of internal wave-field parameters that were used to compute sound-speed distributions. Numerical results include estimates of the full-field and modal-intensity fluctuations, as well as the spatial coherence at two vertical arrays located at 33 and 45 km from the moored sources. [Work supported by NRL and ONR. The authors wish to acknowledge the contribution of the SWARM group to this work.]

ASA 132nd meeting - Hawaii, December 1996