Estimation of the characteristics of wave propagation in the water pipe using continuous wavelet transform

Correlation analysis has been widely used in pipeline leakage localization, and leakage noise correlators have been developed. The reliability of this technology for leakage location depends mainly on the propagation characteristics of the leakage signal, including the acoustic wave speed along the pipeline and the attenuation with distance. The leakage signal is mainly carried by a predominantly fluid-borne wave and propagates along the pipeline. Its propagation property is greatly influenced by the pipeline parameters, surrounding medium parameters, and et al. Although nearly all the required parameters can be obtained employing some measurements, it is still inconvenient, even, these parameters are often unable to be obtained due to the roads and buildings above. For most pipeline systems, it is also not allowed to install test equipment inside the pipe to test the propagation characteristics of acoustic waves. A test and analysis technique of acoustic wave propagation characteristics for the fluid-filled pipe is put forward, this method used acoustic waves generated by the release of a fire hydrant as excitation and applied the wavelet transform to distinguish the release signals at different characteristic frequencies. The theory of the method was derived in detail and the feasibility was tested and verified. The test results show that the proposed method can estimate the propagation characteristics at the low-frequency. Due to the low SNR of the test signals at the high-frequency and the complexity of the acoustic wave propagation pathway, the wavenumber estimation values are found to fluctuate. This method provides a feasible way to test the propagation characteristics of the fluid-filled pipe.