Excitation techniques for nonlinear acoustic landmine detection

Abstract

Nonlinear acoustic landmine detection techniques are currently being investigated. These detection methods employ two tones broadcast in the vicinity of a buried mine. Measurement of the resultant surface velocity yields a spectrum rich in nonlinearly generated combination frequencies. The nonlinear mechanism governing the mine/soil interface is not completely understood. Donskoy et al. have proposed that a discontinuity occurs when the mine/soil system is subjected to acoustic excitation. [Donskay etal, J. Acoust. Soc. Am. 111, 2705–2714 (2002)] In this case, the mine and soil remain in contact during compression, but separate in tension. Concurrently, Korman and Sabatier have documented nonclassical nonlinear effects in conjunction with acoustic mine detection [Korman etal, J. Acoust. Soc. Am. 116, 3354–3369 (2004)]. Specifically, they have observed conditioning, soil dynamics, and hysteresis. These results are consistent with those of geomaterials which exhibit mesoscopic elasticity. It is likely that the nonlinear response above a buried mine is a function of both classical and nonclassical effects. These experiments investigate the amplitude dependence of nonlinear effects above a buried mine as a function of linear velocity. A comparison of the nonlinear amplitude dependence in the presence of a mine versus soil alone is intended to provide insights into the nature of the mine/soil interface.