Discrete-mode source development and testing for new seismo-acoustic sonar
By: Frederick E. Gaghan, Jr
Publisher: Naval Postgraduate School; Available from National Technical Information Service
Published: 1998
Place of publication: Monterey, Calif; Springfield, Va
Language: eng
Number of pages: 182
Description: A seismo-acoustic sonar concept that uses guided interface waves (Rayleigh or Scholte) is being developed to      detect buried ordnance in the sea floor and beach sediments. This thesis describes the initial research conducted      into the design, construction, and field testing of possible seismic sources that excite preferentially the interface      waves desired for use in such a system. The theory of elasticity shows that seismic interface waves have elliptical      particle velocity orbits in the vertical plane along the path of propagation. It was therefore decided that to      selectively excite the desired interface waves, a harmonic source employed at the interface must induce elliptical      particle motion in this plane. Several exploratory sources were developed to produce this type of excitation.      Field tests of the discrete-mode sources developed were conducted to evaluate this hypothesis, but due to the      non-optimum nature of the experimental sources, perfect discrete source excitation was not obtained. However,      it was found that the medium itself acted as a selective filter for the interface waves after a few tens of meters of      propagation. The experimental results obtained here suggest that the basic concept of discrete-mode excitation      looks promising.
Notes: Thesis advisor(s): Steven R. Baker, Thomas G. Muir.

"March 1998."

Thesis (M.S. in Physics and M.S. in Engineering Acoustics)--Naval Postgraduate School, March 1998.

Includes bibliographical references (p. 179-180).

"Approved for public release, distribution unlimited"--Cover.

Also available online.

Mode of access: World Wide Web.

System requirements: Adobe Acrobat reader.

US Navy (USN) author.

dk/dk cc:9116 7/23/98.