Synthetic aperture experiment in the Hudson Canyon area

Abstract

In 1988, narrow-band sound propagation measurements were performed in 73 m of water on the New Jersey Continental Shelf over a frequency range from 50 to 600 Hz. A mid-depth source was towed past a 24-element hydrophone array out to ranges of approximately 4 km. Precision time bases controlled the source and were recorded on one of the data channels. A Del Norte radar system measured the range to within several meters accuracy. Plots of the residual phase of the sound pressure as a function of range demonstrate the high quality of the data. A synthetic aperture technique was used to produce horizontal wave-number spectra at each of the hydrophone depths. Plots of the magnitude of the horizontal wave number as a function of depth and wave number clearly demonstrate the modal nature of the propagation. The sound speed in the water column was calculated from CTDs taken during the experiment, and the second speed in the bottom was derived using an acoustical inversion technique. The measured acoustical data along with the measured and derived environmental information provide a unique data set for testing processing and modeling algorithms. [Work supported by ONR.]