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Characterisation of high frequency, high amplitude sonar fields using optical measurement of transducer surface velocity

Humphrey, V F*; Robinson, S P; Theobald, P D; Cooling, M P* (2007) Characterisation of high frequency, high amplitude sonar fields using optical measurement of transducer surface velocity. In: Proceedings of the 2nd International Conference & Exhibition on "Underwater Acoustic Measurements: Technologies & Results", 2007, Crete.

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Abstract

Scanning Laser Doppler Vibrometers provide a convenient method of measuring the magnitude and phase of the surface velocity of transducers operating in water at frequencies of hundreds of kilohertz. This optical approach is relatively rapid and non-perturbing with a good spatial resolution. In addition to directly characterising the vibrational behaviour of the transducer this approach provides two-dimensional data that can be numerically propagated to predict the entire pressure field of the transducer. This approach is illustrated for a number of transducers over a frequency range from 100 kHz to 500 kHz, with a commercial scanning vibrometer being used to measure the devices with a spatial resolution of better than half an acoustic wavelength. The surface velocity data is used to predict the acoustic field at various ranges and the results are shown to be in generally very good agreement with a range of field measurements obtained by hydrophone scanning. An added advantage of this approach is that for high drive levels the optical data can be used as the basis of the input to a nonlinear propagation code, based on the Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation, to predict the nonlinear propagation and resulting additional attenuation.

Item Type: Conference or Workshop Item (UNSPECIFIED)
Keywords: Underwater acoustics, optical methods, sonar, nearfield
Subjects: Acoustics
Acoustics > Underwater Acoustics
Last Modified: 02 Feb 2018 13:15
URI: http://eprintspublications.npl.co.uk/id/eprint/3938

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