Measurement of Ocean Bottom Reflection Loss with a Horizontal Line Array
This paper presents a comparison between two experimental techniques of measurement of reflection loss versus ocean bottom grazing angle for estimation of the compressional and shear speeds of the upper crust basalt. One technique uses a conventional expanding spread geometry; its advantage is that a single sea floor site is ensonified at all angles. The other technique introduces a broadside reflection geometry that enables measurement of the first bottom reflection at the specular angle; in this configuration, the reflectivity is sampled at different sea floor sites for each angle. Both techniques involve two ships, a source ship to deploy impulsive sound sources and a second ship to tow a horizontal line array. The experiments were carried out in deep water (∼ 5 km) at a site in the North Pacific where a thin layer of sediment covered upper crust basalt. The data were processed to provide reflection loss versus angle in a third-octave frequency band centred at 8 Hz. The comparison of the two techniques was based on the results of Bayesian inversion of the reflectivity data to infer model parameters of a geoacoustic model for the bottom at the experimental site. The inversion results indicate that the reflection loss data are most sensitive to the sediment layer thickness and the compressional and shear speeds of the basalt, and show that both techniques give similar values for the sensitive model parameters.
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Document Type: Research Article
Publication date: July 1, 2016
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- Acta Acustica united with Acustica, published together with the European Acoustics Association (EAA), is an international, peer-reviewed journal on acoustics. It publishes original articles on all subjects in the field of acoustics, such as general linear acoustics, nonlinear acoustics, macrosonics, flow acoustics, atmospheric sound, underwater sound, ultrasonics, physical acoustics, structural acoustics, noise control, active control, environmental noise, building acoustics, room acoustics, acoustic materials, acoustic signal processing, computational and numerical acoustics, hearing, audiology and psychoacoustics, speech, musical acoustics, electroacoustics, auditory quality of systems. It reports on original scientific research in acoustics and on engineering applications. The journal considers scientific papers, technical and applied papers, book reviews, short communications, doctoral thesis abstracts, etc. In irregular intervals also special issues and review articles are published.
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