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Modelling acoustic signals containing reflections in the calibration of underwater acoustic transducers in laboratory tanks.

Robinson, S P; Harris, P M (2000) Modelling acoustic signals containing reflections in the calibration of underwater acoustic transducers in laboratory tanks. NPL Report. CMAM 52

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Abstract

In the calibration of an underwater electroacoustic transducer, the stepped-sinusoidal signals that are commonly used are contaminated by transients due to the resonant behaviour of the transducer as well as noise. In addition, when calibrations are undertaken in reverberant laboratory tanks of finite size, reflections from the tank boundaries often arrive before the steady-state response of the transducer can be observed directly.
Previous work has incorporated the use of signal modelling to predict the steady-state response from the initial transient-dominated part of the waveform prior to the arrival of reflections. The approach used was to model the free-time response of the device by a function consisting of a sum of complex exponential terms which were used to describe both the steady-state and resonant behaviour of the device. However, benefits may be expected, particularly for high-Q devices, from extending the time-window for the signal modelling into the region containing reflections.
In this report, models are described for acoustic signals that account both for the transient behaviour of the devices as well as the effects of reflections. Also described are the data processing algorithms for estimating values for the parameters in these models from measurement data in the cases where, firstly, the arrival times for the reflections are known and, secondly, they are regarded as additional parameters to be determined. Results are presented of applying these algorithms to analyse simulated data representing the measured response of a device as well as data obtained from measurements of real transducers.
This work described in this report was undertaken as part of project 3.1.7 of the 1999-2002 NMS Acoustics Metrology Programme.

Item Type: Report/Guide (NPL Report)
NPL Report No.: CMAM 52
Subjects: Acoustics
Acoustics > Underwater Acoustics
Last Modified: 02 Feb 2018 13:17
URI: http://eprintspublications.npl.co.uk/id/eprint/1590

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