Parametric acoustic conversion in ocean sediments

Abstract

The interaction of acoustic waves from a parametric acoustic array at a water‐sediment interface has been studied theoretically. This investigation was motivated by the observation of better penetration of acoustical energy into sediments using a parametric acoustic array rather than a conventional source [T. G. Muir, C. W. Horton, Sr., and L. A. Thompson, J. Sound Vib. 64, 539 (1979)]. In order to treat the nonlinear interaction of sound waves in a sediment, the inhomogeneous elastic wave equation for a solid was solved. One effect of the nonlinear terms in this equation is the coupling of compressional and shear waves. The separation of the coupling effect is shown. The primary waves from a parametric source are expected to excite Stoneley waves along the water‐sediment interface. The Stoneley waves are assumed to serve as a source for parametric acoustic conversion in the sediment. The analytic solutions of the inhomogeneous wave equation are spherical waves modified by an angular dependence in the amp...