title: Horizontal ducting of sound by curved nonlinear internal gravity waves in the continental shelf areas.
abstract: The acoustic ducting effect by curved nonlinear gravity waves in shallow water is studied through idealized models in this paper. The internal wave ducts are three-dimensional, bounded vertically by the sea surface and bottom, and horizontally by aligned wavefronts. Both normal mode and parabolic equation methods are taken to analyze the ducted sound field. Two types of horizontal acoustic modes can be found in the curved internal wave duct. One is a whispering-gallery type formed by the sound energy trapped along the outer and concave boundary of the duct, and the other is a fully bouncing type due to continual reflections from boundaries in the duct. The ducting condition depends on both internal-wave and acoustic-source parameters, and a parametric study is conducted to derive a general pattern. The parabolic equation method provides full-field modeling of the sound field, so it includes other acoustic effects caused by internal waves, such as mode coupling/scattering and horizontal Lloyd's mirror interference. Two examples are provided to present internal wave ducts with constant curvature and meandering wavefronts.
authors.affiliation: Applied Ocean Physics and Engineering Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA. ytlin@whoi.edu
authors.forename: Ying-Tsong
authors.initials: YT
authors.lastname: Lin
authors.forename: Kara G
authors.initials: KG
authors.lastname: McMahon
authors.forename: James F
authors.initials: JF
authors.lastname: Lynch
authors.forename: William L
authors.initials: WL
authors.lastname: Siegmann
mesh_terms: D000162:Acoustics; D003198:Computer Simulation; D019015:Geologic Sediments; D006112:Gravitation; D009038:Motion; D017711:Nonlinear Dynamics; D009716:Numerical Analysis, Computer-Assisted; D009792:Oceans and Seas; D013016:Sound; D014867:Water; D014872:Water Movements
chemical_list: D014867:Water