Nonlinear Acoustic Experiments Involving Landmine Detection: Connections with Mesoscopic Elasticity and Slow Dynamics in Geomaterials

Abstract

The vibration interaction between the top‐plate of a buried VS 2.2 plastic, anti‐tank landmine and the soil above it appears to exhibit similar characteristics to the nonlinear mesoscopic/nanoscale effects that are observed in geomaterials like rocks or granular materials. [J. Acoust. Soc. Am. 116, 3354–3369 (2004)]. When airborne sound at two primary frequencies f1 and f2 (closely spaced near resonance) undergo acoustic‐to‐seismic coupling, (A/S), interactions with the mine and soil generate combination frequencies | n f1 ± m f2 | which affect the surface vibration velocity. Profiles at f1, f2, f1 −(f2 − f1) and f2 +(f2 − f1) exhibit single peaks whereas other combination frequencies may involve higher order modes. A family of increasing amplitude tuning curves, involving the surface vibration over the landmine, exhibits a linear relationship between the peak particle velocity and corresponding resonant frequency. Subsequent decreasing amplitude tuning curves exhibit hysteresis effects. New experiments f...