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A comparison of free-field calibration techniques for hydrophones using the reciprocity and optical methods.

Theobald, P D; Robinson, S P (2007) A comparison of free-field calibration techniques for hydrophones using the reciprocity and optical methods. In: 2nd International Conference & Exhibition on "Underwater Acoustic Measurements: Technologies & Results", June 2007, Crete.

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Abstract

One of the most important methods of validating a primary standard is to compare with another independent absolute calibration method, preferably one based on a different physical principle (and therefore with few common sources of uncertainty). The UK National Physical Laboratory has established two primary standard methods for the free-field calibration of hydrophones. In the frequency range 500 kHz to 20 MHz, the primary standard is realised using optical interferometry; in the range from 1 kHz to 500 kHz, it is realised by the method of three-transducer spherical-wave reciprocity. In addition, NPL is working to devise a new calibration method for the lower frequency range based on laser vibrometry. Although the ranges of the two primary standards are defined as above, both methods can be used in the frequency range 200 kHz to 1 MHz, enabling a comparison to be undertaken between these two independent methods. For the optical method based on laser vibrometry, a comparison is possible with the reciprocity method throughout most of the applicable frequency range. In general, excellent agreement has been achieved with the differences observed being within combined uncertainties.

Item Type: Conference or Workshop Item (UNSPECIFIED)
Keywords: Hydrophone, calibration, interferometry
Subjects: Acoustics
Acoustics > Underwater Acoustics
Last Modified: 02 Feb 2018 13:15
URI: http://eprintspublications.npl.co.uk/id/eprint/3919

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