Acoustic detection of mines buried in the sediment in shallow waters using a laser Doppler vibrometer.

Abstract

Naval operations in littoral regions require accurate methods and sensors to detect mines, thereby preventing injury to personnel and damage to equipment. Mines may be buried in the sediment in shallow waters, on beaches, or regions adjacent to the water. Acoustic detection of a mine buried in the seabed involves two major issues: exciting the vibration of a mine and measuring the vibration response of the mine and the environment. A small laboratory‐like testing facility, a loudspeaker, and a laser Doppler vibrometer (LDV) were used in experiments to detect buried mines in sand and under water. Two possible scenarios for measurement of the vibration response of a mine and the environment were used: sensing vibration of the water surface and sensing vibration of the sand surface. The on‐mine and off‐mine mechanical impedances were measured with the LDV. The possibility of the transmission of the mine’s vibration to the surface of the water where it can be measured with an LDV was demonstrated. In these experiments, glass beads were suspended on the water surface to improve the reflected light returning to the LDV. Test results are presented and discussed. [Work supported by the Office of Naval Research Grant N00014‐09‐1‐0016.]