The use of a sparse planar array sensor for measurement of the acoustic properties of panel materials at simulated ocean conditions

Abstract

Characterisation of the acoustic properties of materials for underwater acoustics is often carried out by measuring the transmitted and/or reflected pressure signals after insonification of a test panel by an incident acoustic wave. For this method to be reliable, the incident and transmitted (or reflected) signals arriving at the hydrophone receiver should be well separated in time (enabling windowing techniques to be applied), and the diffracted signals from the panel edge should not contaminate the measured signal. At low kilohertz frequencies, these conditions are difficult to achieve for the size of panel and test tank commonly available. This paper describes a method for discriminating against the diffracted signals by use of a planar array of hydrophones as the receiver. The sound source used for the method is a parametric array to provide some source directivity and to provide short broadband signals for analysis. The method is demonstrated by application to the measurement of reflection loss and transmission loss for test panels at frequencies of 1 kHz to 10 kHz under simulated ocean conditions using a specialised test chamber capable of controlling the water temperature and hydrostatic pressure during measurements. A comparison is shown with results obtained with a single hydrophone, and a discussion is given of the number and position of hydrophones in the array.

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ORCID for Victor F. Humphrey: orcid.org/0000-0002-3580-5373

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