An experimental study of acoustic forward and backscattering using a scale model of Arctic ice ridges

• Main Author: Williams, Hollis Edward Fitzgeraldet al
• Other Authors: American University (degree granting institution.)
• Format: Thesis
• Language: English
• Published: American University 2017
• Subjects: Acoustics; Physical oceanography; Arctic; Arctic Ocean; Broad Peak
• Online Access: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqm&rft_dat=xri:pqdiss:9303321; http://hdl.handle.net/1961/thesesdissertations:2676; https://auislandora.wrlc.org/islandora/object/thesesdissertations%3A2676/datastream/TN/view/experimental%20study%20of%20acoustic%20forward%20and%20backscattering%20using%20a%20scale%20model%20of%20Arctic%20ice%20ridges.jpg

There is continuing interest in understanding the propagation of sound in the Arctic Ocean. The location of sound sources in the Arctic Ocean and the mapping of the ice-water interface both use the scattering of acoustic data and its analysis. The better the analysis model, the better the source location and mapping. This paper reports on the development of an experimental system for scale modeling of Arctic ice ridges. This system measures the forward and backward scattered waves from acoustically "soft" protuberances at ka = 0.67. The new experimental system examines the Burke-Twersky mathematical theory applied to ocean acoustic wave scattering. The experiment implements the geometry of the Twersky model in its evaluation. The Diachok geometric model was used for the bottom cross-section of an Arctic ice keel. The system measured the reflection coefficient of a scattered wave. This systematic approach studied the scattering from a single ridge, with varying incident-grazing angles, and two different azimuthal orientations. Scattering from a full random scale model was also measured. The experimental technique involved a large diameter to wavelength ratio for the transducer insonifying the model. Multiple point transducers received scattered signals. Several receivers were positioned to measure the scattering simultaneously. The size of the receivers also made it possible to measure the acoustic signal at angles close to the transmitting angle. The data for the single ridge with perpendicular azimuth was compared directly to the differential scattering function of the Twersky model. Favorable results were found. The experimental system successfully measures the angular dependence of the Twersky model. The expected broad peak exists at the 90$\sp\circ$ grazing receiving angle and the expected variations exists with differing incident-grazing angle. The system allows testing of other aspects of the Burke-Twersky theory. Also, other elements of under-ice scattering can be modeled by the system. Source: Dissertation Abstracts International, Volume: 53-10, Section: B, page: 5247. Ph.D. American University 1992. English