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A systematic assessment of the 'magnomic' method of high frequency hydrophone calibration.

Zeqiri, B; Gelat, P N; Hodnett, M (1999) A systematic assessment of the 'magnomic' method of high frequency hydrophone calibration. NPL Report. CMAM 26

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Abstract

This document represents the technical report for Milestone (d) of Project 2.3(i) of the DTI NMS Acoustics Programme for 1995-1998 entitled "Establish service for hydrophone calibration in the frequency range 20 to 60 MHz". The actual title of Milestone (d) is "Validate interferometer calibration method by use of the magnomic calibration method."
The aim of this Milestone was to attempt to corroborate hydrophone calibrations based on the NPL primary standard laser interferometer, by using an independent technique termed the 'magnomic' method. This method utilises the theoretical modelling of propagating acoustic waves of finite amplitude within the plane-wave region of a 10 MHz transducer. This document describes in detail a number of aspects of the theoretical and experimental work carried out. The plane-wave algorithm used to predict the acoustic waveform at various measurement positions is presented. An important facet of the work has been an investigation of the pressure distribution generated by the transducer at various distances from the transducer face through beam-plotting, work which has demonstrated significant departures from the required plane-wave behaviour. Also presented are the results of experimental studies of other aspects of the 'magnomic' calibration method.
Finally, calibration results are presented for four Marconi membrane hydrophones covering the frequency range 10 to 60 MHz. Derived sensitivity values are compared with those obtained from a range of other methods, including the NPL primary standard laser interferometer. The main conclusion drawn from the studies is that the 'magnomic' calibration method is not currently appropriate for use as a standard high frequency calibration technique.

Item Type: Report/Guide (NPL Report)
NPL Report No.: CMAM 26
Subjects: Acoustics
Acoustics > Underwater Acoustics
Last Modified: 10 Sep 2018 14:35
URI: http://eprintspublications.npl.co.uk/id/eprint/1057

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