Novel Acoustic Scattering Processes for Target Discrimination [report]

Philip L. Marston
2008 unpublished
LONG TERM GOALS This is part of the Shallow-Water Autonomous Mine Sensing Initiative (SWAMSI) to improve the reliability of acoustic methods using a wide frequency range and scattering data not necessarily limited to monostatic signatures. OBJECTIVES The objective of this grant is to examine issues supportive of the SWAMSI team effort by improving the understanding of acoustic scattering processes relevant to MCM and the shallow water environment. The current emphasis is on the interpretation
more » ... he interpretation of bistatic synthetic aperture sonar images. An example of another issue investigated at Washington State University is the scattering of sound by a plastic truncated cone. The cone material and shape were selected to be relevant to high frequency signatures of certain explosive-filled mines. Other objectives involved improved understanding and modeling of scattering mechanisms that are broader in scope and are outlined below. APPROACH A multifaceted research approach appears to be advisable because some acoustic strategies may not always be applicable and different strategies may require widely different amounts of time to acquire the needed data for a given potential mine field. Consequently it appeared to Marston that the SWAMSI program should retain research components that support both low frequency and high frequency sonar technologies. It would be potentially useful to understand which features of the scattering are important for discriminating between live (explosive-filled) targets and decoy targets containing other materials. Commonly used explosives have some similarity to certain solid plastics in their acoustic properties: (1) both materials have longitudinal wave speeds greater than the speed of sound in sea water, but less than rocks, cement, or metals: (2) in many cases both materials have shear wave velocities less than the speed of sound in sea water. The approach has several activities. Many of these were summarized in the annual report submitted in September 2005 [1]. The current report will emphasize the principal activities for FY2006. These activities were: (1) Improved apparatus for laboratory based acquisition of scattering data: With the partial support of this grant and other ONR grants (N000140310583 and N000140310585) significant improvements were made to our 7000-gallon facility used to acquire monostatic and bistatic scattering data at Washington State University. The changes involve improved computer control of data acquisition as well as the ability to scan the position of a receiving hydrophone over a wide range of scattering angles. The list of activities noted below concern tasks primarily associated with grant Same as Report (SAR) 18. NUMBER OF PAGES 9 19a. NAME OF RESPONSIBLE PERSON a. REPORT unclassified b. ABSTRACT unclassified c. THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18
doi:10.21236/ada533117 fatcat:bwlappwjkbddppt7zciosuodvm