Nonlinear acoustic detection of buried landmines: A tribute to Joe Blue

Abstract

As a graduate student at Brown University (∼1978), this researcher was very fortunate to have met Joe Blue at Acoustical Society meetings. As I had little knowledge of the members in the society and an extremely limited grasp of the practical technology behind nonlinear acoustics, Joe was extremely friendly and took the time to answer a long list of questions about nonlinear underwater transducer designs with applications to the parametric array [Muir, T.G. & Blue, J.E. ‘‘Experiments on the acoustic modulation of large-amplitude waves,’’ J. Acoust. Soc. Am. 46, 227–232 (1969)]. This influenced this researcher’s Ph.D. thesis involving experiments on the scattering of sound by sound in the presence of turbulence. Recently, experiments on the nonlinear acoustic detection of buried landmines [Korman, M.S. & Sabatier, J.M., ‘‘Nonlinear acoustic techniques for landmine detection,’’ J. Acoust. Soc. Am. 116, 3354–3369 (2004)] has brought some attention to understanding the difference between classical and nonclassical nonlinearity. As a tribute to Joe Blue, the latest results will be presented involving the connections to mesoscopic nonlinear elasticity and slow dynamics in nonlinear buried landmine detection. Here, tuning curve behavior of the soil-surface vibration over a landmine exhibits a linear decrease in resonant frequency with increasing amplitude. Two-tone test excitation reveals a rich spectrum of combination frequency components useful in detection schemes.