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Amplitude distortion of measured leak noise signals caused by instrumentation: effects on leak detection in water pipes using the cross-correlation method

Amplitude distortion of measured leak noise signals caused by instrumentation: effects on leak detection in water pipes using the cross-correlation method
Amplitude distortion of measured leak noise signals caused by instrumentation: effects on leak detection in water pipes using the cross-correlation method

A common way to detect and locate leaks in buried water pipes is to use leak noise correlators. Vibration or acoustic signals are measured on or in the pipe using sensors placed either side of the leak, and the difference in the leak noise arrival times (time delay) at the sensors is estimated from the peak in the cross-correlation function of these signals. Over many years, much effort has been spent on improving the quality of the leak noise signals with the aim of improving the time delay estimate. In this paper it is shown that even if the signals suffer from severe amplitude distortion through either clipping or quantization, then an accurate time delay estimate can be obtained provided that the zero crossings in the noise data are preserved. This is demonstrated by using polarity co-incidence correlation on simulated and measured data. The use of random telegraph theory is also used as an approximation to allow the derivation of approximate analytical solutions for the cross-correlation function and cross spectral density of clipped noise to facilitate further insight into the effects of severe clipping.

Clipping, Leak noise correlation, Quantization, Water leak detection
0022-460X
Brennan, M. J.
87c7bca3-a9e5-46aa-9153-34c712355a13
Gao, Y.
d209d667-ef6e-4a24-ab7d-2f52c618361f
Ayala, P. C.
3984aae7-7ca5-4c5c-876c-97ca7be98c93
Almeida, F. C.L.
f3e961f9-05ea-49cd-aa82-20e421de7b8c
Joseph, P. F.
9c30491e-8464-4c9a-8723-2abc62bdf75d
Paschoalini, A. T.
bfa1fed9-f566-4380-807a-2c53e01b6627
Brennan, M. J.
87c7bca3-a9e5-46aa-9153-34c712355a13
Gao, Y.
d209d667-ef6e-4a24-ab7d-2f52c618361f
Ayala, P. C.
3984aae7-7ca5-4c5c-876c-97ca7be98c93
Almeida, F. C.L.
f3e961f9-05ea-49cd-aa82-20e421de7b8c
Joseph, P. F.
9c30491e-8464-4c9a-8723-2abc62bdf75d
Paschoalini, A. T.
bfa1fed9-f566-4380-807a-2c53e01b6627

Brennan, M. J., Gao, Y., Ayala, P. C., Almeida, F. C.L., Joseph, P. F. and Paschoalini, A. T. (2019) Amplitude distortion of measured leak noise signals caused by instrumentation: effects on leak detection in water pipes using the cross-correlation method. Journal of Sound and Vibration, 461, [114905]. (doi:10.1016/j.jsv.2019.114905).

Record type: Article

Abstract

A common way to detect and locate leaks in buried water pipes is to use leak noise correlators. Vibration or acoustic signals are measured on or in the pipe using sensors placed either side of the leak, and the difference in the leak noise arrival times (time delay) at the sensors is estimated from the peak in the cross-correlation function of these signals. Over many years, much effort has been spent on improving the quality of the leak noise signals with the aim of improving the time delay estimate. In this paper it is shown that even if the signals suffer from severe amplitude distortion through either clipping or quantization, then an accurate time delay estimate can be obtained provided that the zero crossings in the noise data are preserved. This is demonstrated by using polarity co-incidence correlation on simulated and measured data. The use of random telegraph theory is also used as an approximation to allow the derivation of approximate analytical solutions for the cross-correlation function and cross spectral density of clipped noise to facilitate further insight into the effects of severe clipping.

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More information

Accepted/In Press date: 13 August 2019
e-pub ahead of print date: 17 August 2019
Published date: 24 November 2019
Keywords: Clipping, Leak noise correlation, Quantization, Water leak detection

Identifiers

Local EPrints ID: 434762
URI: http://eprints.soton.ac.uk/id/eprint/434762
ISSN: 0022-460X
PURE UUID: 1edb8398-2c60-4c33-a513-9d05bfce6fb0

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Date deposited: 08 Oct 2019 16:30
Last modified: 07 Oct 2020 06:39

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Contributors

Author: M. J. Brennan
Author: Y. Gao
Author: P. C. Ayala
Author: F. C.L. Almeida
Author: P. F. Joseph
Author: A. T. Paschoalini

University divisions

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