Shallow-Water Acoustics

William A. Kuperman, James F. Lynch
2004 Physics today  
Inversion methods based on spatial coherence of multi-tone CW data have been applied extensively in underwater acoustics to estimate geoacoustic profiles. This paper presents results for a different approach based on broadband waveform inversion at a single hydrophone. The inversion is formulated as an optimization problem to determine the geoacoustic model that provides the best fit between calculated and measured waveforms. A hybrid simulated annealing algorithm is used to search the
more » ... ensional model parameter space. The method is applied to data from the INTIMATE98 shallow water experiment to estimate the sound speed and density at the sea floor. 2. Much is known about deep ocean ambient noise, rather less about the more highly structured and variable noise in temperate coastal waters, and rather little about the tropical shallow waters that include coral reefs and the biological diversity these ecosystems support. Interest in shallow water acoustics has been growing over the last decade, and more recently specific interest has bloomed in tropical shallow water and the features particular to these areas. As sonar systems and operations become more complex, moving towards the use of ambient noise and the need for communicating via networked acoustic modems in noisy environments, the soundscape of shallow waters has become more important. This paper presents some of the challenges and advantages of tropical shallow water acoustic environments, and makes some geographic comparisons. While some aspects of tropical ambient noise make life more difficult, such as the non-Gaussian energy distribution of snapping shrimp noise, other aspects are seen to be quite robust, such as the very similar pulse signatures of snapping shrimp over widelyseparated regions. The development of signal processing tools based on wavelet and other compact transforms to deal with the detection, separation, and classification of overlapping tropical shallow water noise sources is discussed.
doi:10.1063/1.1825269 fatcat:bclxnqxsvnh5tfjfgg2viseiau