Acoustic features of sharp and continuous three-dimensional curved coastal fronts

Abstract

Three-dimensional curved shelf-slope fronts have been modeled with sharp [Lin and Lynch, J. Acoust. Soc. Am. (2012)] and continuous [DeCourcy et al., J. Acoust. Soc. Am. (2016)] sound speed changes. For the sharp front, expressions were found for determining dependence of acoustic quantities such as modal speeds on feature-model parameters. Asymptotic approximations are used to simplify terms in the dispersion relation for the horizontal wavenumber, and further analysis leads to convenient and accurate formulas for the parameter dependence. Corresponding results will be presented for the continuous front, which possesses a different class of acoustic modes known as tunneling modes that carry larger amounts of energy across and along the front than other modes. Results for both frontal models will be discussed, comparing and contrasting characteristics including wavenumber distributions, mode types, and parameter dependences. An important goal is to examine the similarities and differences for sharp or continuous fronts in the sensitivity of acoustic quantities to feature parameters, such as front location and width, bottom slope angle, and source frequency. This would permit identification of situations where the more convenient sharp front model is appropriate. [Work supported by ONR Grants N00014-14-1-0372 and N00014-11-1-0701.]