The contribution of normal modes in the bottom to the acoustic field in the ocean
MetadataShow full item record
The effects of normal modes in the bottom on the acoustic field in the ocean are examined. The ocean bottom model consists of a slow isovelocity layer overlying an isovelocity half-space to simulate the characteristic sound velocity drop at the water-bottom interface. Attention is focused on the perfectly trapped modes which are excited in the layer by inhomogeneous waves emitted by a point source in the water column. The relative normal mode contribution to the total acoustic field in the water is calculated analytically for a near-bottom source/receiver geometry and evaluated for representative ocean bottom examples. It is shown that, for combined source/receiver heights less than a wavelength, the field is dominated by the leaky mode contribution at short ranges ( $ 2 km) and the trapped mode contribution at long ranges ( ~ 2 km). For fixed bottom parameters, the trapped mode contribution increases exponentially with decreasing combined source/receiver height. It is also shown that, for a fixed layer wavenumber-thickness product and fixed layer sound speed, the leaky mode fields at different frequencies are approximately range-scaled versions of the same field.
Also published as: Journal of the Acoustical Society of America 68 (1980): 602-612
Suggested CitationTechnical Report: Macpherson, Mark K., Frisk, George V., "The contribution of normal modes in the bottom to the acoustic field in the ocean", 1981-04, DOI:10.1575/1912/10241, https://hdl.handle.net/1912/10241
Showing items related by title, author, creator and subject.
Udovydchenkov, Ilya A.; Stephen, Ralph A.; Duda, Timothy F.; Bolmer, S. Thompson; Worcester, Peter F.; Dzieciuch, Matthew A.; Mercer, James A.; Andrew, Rex K.; Howe, Bruce M. (Acoustical Society of America, 2012-10)Data collected during the 2004 Long-range Ocean Acoustic Propagation Experiment provide absolute intensities and travel times of acoustic pulses at ranges varying from 50 to 3200 km. In this paper a subset of these data ...
Casey, Kevin D. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1988-06)Two approaches to determining the ocean sound speed profile using measured acoustic modal eigenvalues are examined. Both methods use measured eigenvalues and mode dependent assumed values of the WKB phase integral as ...
The Woods Hole Oceanographic Institution digital ocean bottom hydrophone instrument : technical report Koelsch, Donald E.; Peal, Kenneth R.; Purdy, G. Michael (Woods Hole Oceanographic Institution, 1982-06)This report describes the design and capabilities of a new ocean bottom hydrophone instrument. The instrument is microprocessor controlled and records digitally on a commercially available cartridge tape recorder with ...