Accession Number:

ADA508897

Title:

Supplemental Student Support: Detection and Identification of Buried Targets using Time Reversal Acoustics

Descriptive Note:

Final rept.

Corporate Author:

BOSTON UNIV MA

Personal Author(s):

Report Date:

2009-11-04

Pagination or Media Count:

283.0

Abstract:

The presence of noise and coherent returns from clutter often confounds efforts to acoustically detect and identify target objects buried in inhomogeneous media. Using iterative time reversal with a single channel transducer, returns from resonant targets are enhanced, yielding convergence to a narrowband waveform characteristic of the dominant mode in a targets elastic scattering response. The procedure consists of exciting the target with a broadband acoustic pulse, sampling the return using a finite time window, reversing the signal in time, and using this reversed signal as the source waveform for the next interrogation. Scaled laboratory experiments 0.4-2 MHz are performed employing a piston transducer and spherical targets suspended in the free field and buried in a sediment phantom. In conjunction with numerical simulations, these experiments provide an inexpensive and highly controlled means with which to examine the efficacy of the technique. Signal-to-noise enhancement of target echoes is demonstrated. The methodology reported provides a means to extract both time and frequency information for surface waves that propagate on an elastic target. Methods developed in the laboratory are then applied in medium scale 20-200 kHz pond experiments for the detection of a steel shell buried in sandy sediment.

Subject Categories:

  • Acoustic Detection and Detectors
  • Target Direction, Range and Position Finding

Distribution Statement:

APPROVED FOR PUBLIC RELEASE