Parameter dependence of acoustic quantities in a nonlinear internal wave duct

Abstract

Parameter dependence of acoustic quantities in a nonlinear internal wave duct BJD, Matt Milone, YTL Ocean features with 3-D spatial variability in shallow water can significantly affect acoustic propagation. One example is a curved front modeled with a discontinuous sound speed change over a sloping shelf [Lin and Lynch, JASA-EL (2012)], which has an extension to a continuous sound-speed change. An approach using normal modes and perturbation approximations yields convenient formulas that show how acoustic quantities depend on environmental parameters [DeCourcy et al., ASA, Salt Lake City (2016)]. Another common 3-D example is nonlinear internal waves, with wave fronts that pairwise can produce acoustic ducting, radiating, and scattering effects often observed in field data. The previous approach is applied to this feature, using a well model with two sound-speed jumps for such a duct [Lin et al., (2013)]. Approximate formulas for acoustic wavenumbers and phase speeds are determined in order to estimate sensitivity to changes in environmental parameters. All mode types will be considered (whispering gallery, fully bouncing, and leaky), highlighting differences from those in the single-front example. [Work supported by ONR Grants N00014-14-1-0372 and N00014-11-1-0701.]