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Absolute calibration of hydrophones immersed in sandy sediment.

Robb, G B N*; Robinson, S P; Theobald, P D; Hayman, Gary; Humphrey, V F*; Leighton, T G*; Lian Sheng Wang*, (2009) Absolute calibration of hydrophones immersed in sandy sediment. J. Acoust. Soc. Am., 125 (5). pp. 2918-2927.

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Abstract

An absolute calibration method has been developed based on the method of three-transducer spherical-wave reciprocity for the calibration of hydrophones when immersed in sandy sediment. Adoption of a co-linear configuration enables the acoustic attenuation within the sediment to be eliminated from the sensitivity calculation. Example calibrations have been performed on two hydrophones inserted into sandy sediment over the frequency range 10 to 200 kHz. Comparison with water-based results shows that the effect of the sediment varied with frequency. In general, a reduction in sensitivity was observed, with average reductions over the frequency range tested of between 3.2 and 3.8 dB with respect to the equivalent water-based calibrations for the two hydrophones tested. Repeated measurements were undertaken to assess the robustness of the method to the influence of sediment disturbance due to the hydrophone insertion process and the presence of the central hydrophone during the measurements. A simple finite element model, developed for one of the hydrophone designs shows good qualitative agreement with the observed differences from water-based calibrations. The method described in this paper will be of interest to all those undertaking acoustic measurements with hydrophones immersed in sediment where the absolute sensitivity is important.

Item Type: Article
Subjects: Acoustics
Acoustics > Underwater Acoustics
Last Modified: 02 Feb 2018 13:15
URI: http://eprintspublications.npl.co.uk/id/eprint/4370

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