Measurements of High Frequency Reverberation in Shallow Water

Abstract

In September 1991, the first of a series of measurements was made with high frequency (≥ 10 kHz) sonar in shallow waters (35–55 m) of Block Island Sound. Approximately 250 sonar echoes were collected with sonar heads mounted on a remotely controlled, submersed system towed by a surface ship over various bottom types. For ten types of transmit waveform, the output from each transducer in the sonars’ (8x8) arrays was individually recorded digitally. Concurrent oceanographic and geologic measurements included vertical and horizontal profiles of conductivity, temperature, and depth (CTD); current; wave height spectra of the sea-surface; side scan sonar mapping and stereo photography of the bottom; ambient noise; bottom cores; underwater video. Air-filled steel spheres were moored at the site as a distributed target for acoustic imaging experiments. Moreover, data have been analyzed to characterize boundary reverberation for two cases representative of the variability encountered during the experiment.