Internal‐ and surface‐wave‐induced fluctuations and frequency spreading in shallow water acoustic propagation over short ranges

During a 2001 ocean acoustics experiment approximately 40 miles west of San Diego, a moored, underwater source at 30‐m depth transmitted a set of narrow‐band tones in the 100–1000‐Hz band to a 32‐element, 992‐m‐long bottom hydrophone array deployed from R/P FLIP. Also deployed about FLIP were multiple, fixed vertical thermistor strings with ambient pressure sensors, and CTD casts. These data provide observations of the effects of a fluctuating ocean environment on acoustics in shallow water (180 m) over short ranges (2.5 km). A series of very long fast Fourier transforms of the received signals reveal time dependence in the frequency spreading about the transmitted frequency. Time series of spatial and temporal coherence estimates show temporal variations in the relatedness of the received signals. The environmental data are used along with physics‐based models of ocean surface and internal waves to predict the signal fluctuation and frequency spreading characteristics. Results of comparison of acoustic o...