A comparison of time delay estimators for the detection of leak noise signals in plastic water distribution pipes

The position of a leak in buried water distribution pipes, may be determined by accurate estimation of the time delay between two measured acoustic signals. By using a model for the wave propagation along plastic pipes, various time delay estimators using cross-correlation are compared in this paper for their ability to locate a leak in plastic pipes. The estimators of interest are the ROTH impulse response, the smoothed coherence transform (SCOT), the WIENER, the phase transform (PHAT) and the maximum likelihood (ML) estimators. For leak detection in buried plastic water pipes it is found that the SCOT estimator is particularly suited to this purpose. The accuracy of the estimators is also discussed. It is found that random errors introduced by random noise on the signal measurements are insignificant compared with the resolution of the time delay estimators imposed by the low-pass filtering characteristics of the pipe. Limited experimental results are presented to support the findings.