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Improvements in the provision of standards for underwater acoustics at simulated ocean conditions.

Beamiss, G A; Hayman, G; Robinson, S P; Thompson, A D (2004) Improvements in the provision of standards for underwater acoustics at simulated ocean conditions. NPL Report. DQL-AC 010

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Abstract

In this report, a description is given of the improvements made to the provision of standards for underwater acoustics at simulated ocean conditions by the UK National Physical Laboratory. The improved techniques now employed to make acoustic measurements in the APV facility are described, and results obtained using the techniques are presented. The engineering modifications made to enhance the mounting and positioning of devices within the test chamber have improved the operational performance of the facility. In addition, improvements have been made to the procedures for the calibration of acoustic transducers and hydrophones by both absolute and relative methods, dramatically increasing the speed of measurements, and to the measurement of transducer electrical impedance. Work has also been undertaken to determine the acoustic properties of the APV test chamber with parameters determined such as the echo-free time as a function of position, reverberation time, ambient noise levels, and the performance of the acoustic absorbers in providing echoreduction.
A novel technique based on signal modelling has been used to extend the frequency range of operation of the APV down in frequency for calibration of high-Q projectors. Finally, the traceability of open-water calibrations at the Wraysbury facility is described. Particular emphasis is placed on methods to account for the variation in response of reference transducers with temperature, and an assessment is made of the current limitations and planned improvements.

Item Type: Report/Guide (NPL Report)
NPL Report No.: DQL-AC 010
Keywords: calibration
Subjects: Acoustics
Acoustics > Underwater Acoustics
Last Modified: 02 Feb 2018 13:16
URI: http://eprintspublications.npl.co.uk/id/eprint/3114

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