Acoustic normal mode fluctuations due to internal waves in the Shallow Water 2006 experiment

Abstract

The Shallow Water 2006 (SW06) experiment was a large-scale acoustic experiment conducted on the New Jersey continental shelf in the summer of 2006 with substantial investment from the Office of Naval Research. The main goal of this experiment was to find a detailed understanding of the waveguide during the propagation of broadband acoustic signals in the presence of internal waves (IW). One month of IW events recorded during this experiment has been reconstructed with the aids of densely deployed thermistor strings and ship-borne X-Band radars. The comprehensive IW measurements enabled the study of the correlation between the IW-induced time-varying environment and the acoustic normal mode fluctuations. During this experiment, an L-shaped hydrophone array was moored inside the area with IW measurements. Acoustic sources transmitting for 7.5 min every 30 min starting on the hour were deployed at the shallow end of the across-shelf path and the outer end of the along-shelf path respectively. The acoustic modal fluctuations in modal arrival time, intensity, temporal coherence, and spatial coherence during the aforementioned IW events are analyzed. The relationship between the modal behavior and IW parameters is investigated and possible IW inversion schemes using acoustic measurements are discussed. [Work supported by ONR322OA.]