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Acoustic characterisation of panel materials under simulated ocean conditions using a parametric array source.

Humphrey, V F*; Robinson, S P; Smith, J D*; Martin, M J*; Beamiss, G A; Hayman, G; Carroll, N L* (2008) Acoustic characterisation of panel materials under simulated ocean conditions using a parametric array source. J. Acoust. Soc. Am., 124 (2). pp. 803-814.

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Abstract

A technique for evaluating the underwater acoustic performance of materials under simulated ocean conditions in a laboratory test facility is described. The method uses a parametric array as a source of sound to insonify the material under test which is in the form of a panel. The measurement technique has been established within a laboratory test vessel capable of simulating ocean depths down to 700 m, with water temperature control in the range from 2 ºC to 35 ºC. Using the methods described here, the reflection loss and transmission loss of the test panel may be determined at frequencies from a few kilohertz to 50 kHz. The use of the parametric array enables wideband measurements to be undertaken with short-duration pulses, and reduces the effects of diffraction from the panel edges. An acoustic filter is used to truncate the array in order to provide a source-free measurement region and simplify the measurement process. The difficulties of establishing a parametric array in the confined space of the vessel are outlined, and the experimental procedures adopted are described. The technique was validated by undertaking measurements on two test objects that have predictable behaviour. The potential of the technique is also illustrated with experimental results for the measurement of echo reduction and transmission loss of test panels in the frequency range from a few kHz to 50 kHz, for hydrostatic pressures of up to 2.8 MPa, and for temperatures of 8.0 ºC and 26 ºC.

Item Type: Article
Keywords: Underwater acoustics, materials characterisation, panel measurements, parametric array
Subjects: Acoustics
Acoustics > Underwater Acoustics
Last Modified: 02 Feb 2018 13:15
URI: http://eprintspublications.npl.co.uk/id/eprint/4196

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