A 24 KHz sonar system is used to probe rock salt. This equipment, originally designed for water, has been modified to see into rocks. A study of coupling fluids was conducted and castor oil, glycerin, and UGL were tested as coupling fluids between the sonar transducer and the rock salt. The best is glycerin which couples a maximum of 80 percent of the sonar energy into the salt. Castor oil and UGL are about equal in coupling efficiency, but noticeably inferior to glycerin. Quarter-wave plates have been designed and built to increase the efficiency of sonar coupling to 100. A single test was unsuccessful. Energy reflected by a mismatch of acoustic impedances in getting the sonar energy into the salt, gives rise to reverberation in the transducer mount. A complete matching will solve both problems of efficient energy transfer and no reverberation. A theoretical analysis of the beamwidth in salt for both glycerin and castor oil revealed a difference in the beams with glycerin being more sensitive than castor oil for signals straight ahead, and less sensitive for signals off to an angle. This was experimentally verified. Thus, the use of two different fluids allows a change of the shape of the beam in the salt and helps to determine the direction of arrival of reflected signals.

  • Corporate Authors:

    Texas A&M University, College Station

    College of Geosciences
    College Station, TX  United States  77843

    National Science Foundation

    Applied Science and Research Applications, 1800 G Street, NW
    Washington, DC  United States  20550
  • Authors:
    • Unterberger, R R
  • Publication Date: 1978-6-1

Media Info

  • Pagination: 113 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00192030
  • Record Type: Publication
  • Source Agency: National Technical Information Service
  • Report/Paper Numbers: NSF/RA-780172 Prog Rpt.
  • Contract Numbers: NSF-APR76-21764
  • Files: TRIS
  • Created Date: Jul 11 1979 12:00AM