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Testing of IEC 61220 criteria using the NPL-developed hydrophone-amplifier model.

Gélat, P N (2003) Testing of IEC 61220 criteria using the NPL-developed hydrophone-amplifier model. NPL Report. CAIR 4

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Abstract

The curve fitting method outlined in Annex A of IEC 61220 describes a simplified procedure intended to correct for the effects of finite hydrophone bandwidth and active element size when determining the peak-positive acoustic pressure in an ultrasonic field. In this report, this method has been tested using four types of ultrasonic measurement systems, comprising resonant, band-limited and wide-band systems. The reference acoustic pressure waveforms used have been theoretically generated and include an asymmetric distorted pressure pulse with 3.5 MHz fundamental frequency, with and without added band-limited white noise, and distorted sinusoidal waveforms, also of 3.5 MHz fundamental frequency. The waveforms are convolved with the impulse responses of the measurement systems resulting in the output voltage. The correction procedure outlined in Annex A of IEC 61220 is then applied to provide an estimate of the peak-positive pressure, which is then compared with the peak-positive pressure of the original acoustic waveform. This report shows that this correction procedure is no substitute for knowledge of the transfer characteristics of the measurement system when it comes to providing an estimate of the peak-positive acoustic pressure, although an exponential curve fit can provide an estimate of the peak-positive acoustic pressure within ± 5% of its true value, provided the system is of sufficient bandwidth to encompass the dominant frequency content of the original pressure waveform and does not cause excessive ringing in the hydrophone voltage waveform.

Item Type: Report/Guide (NPL Report)
NPL Report No.: CAIR 4
Keywords: ultrasonics
Subjects: Acoustics
Acoustics > Underwater Acoustics
Last Modified: 02 Feb 2018 13:16
URI: http://eprintspublications.npl.co.uk/id/eprint/2697

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