Temporal coherence of acoustic signals propagating through the near surface bubble layer

Abstract

The influence of the near surface bubble layer on the temporal coherence of high frequency acoustic signals over intervals ranging from a few seconds to tens of hours have been investigated experimentally. Acoustic data were collected during the broadband coherence experiment conducted in July 2002 off the coast of San Diego in a water depth of 1000 m. Signals transmitted include short pure tone pulses and broadband (up to 22 kHz) linear frequency modulated (LFM) sweeps centered at 20, 40, and 60 kHz. The projector and receiver hydrophone were suspended from FLIP. Environmental measurements included a towed CTD string, water temperature at a fixed point, near surface bubble layer using a multibeam sonar, current speed and direction, directional wave height and wind speed. [Work supported by ONR Code 321US under the ARL Program.]