Azimuthal Dependent Sound Propagation in Shallow Water Waveguides.
The shallow water environment is a complicated layered media, composed of both range- and depth-dependent inhomogeneities. In light of the many environmental variabilities, it is hypothesized that variations in the acoustic field are both azimuthally and frequency dependent. The physical mechanisms of interactions between broadband acoustic signals and shallow water seabeds are examined. In particular, the azimuthal dependence of sound propagation in shallow water waveguides is addressed. To examine the stated hypothesis, calibrated acoustic experiments were conducted in a shallow water waveguide region where ground truth information is available from a previous geological investigation. A quantitative relationship for acoustic wave and seafloor interactions is developed by employing various signal processing techniques to extract the fundamental information from measured acoustic signals in the field. The signal processing techniques employed in these analyses are as follows: phase variability, instantaneous frequency, and the combined Wavelet Transform and Singular Value Decomposition for modal analysis. Results show that the broadband sound propagation is significantly azimuth dependent in terms of wavefront dispersion characteristics, average of instantaneous frequency, optimum frequency, modal structure, and group velocity. The phase variability, ratio of ground to waterborne waves, and transmission loss only show a slight azimuth dependent. Since the selected shallow water waveguide is representative of continental shelf coastal regions, these results may apply to shallow water waveguides in general.
- Pub Date:
- January 1995
- Engineering: Marine and Ocean; Physics: Acoustics; Geophysics