8 Acoustic Emission and Dual-Tree Complex Wavelet Transform …
91
increases, the acoustic wave was attenuated and became more dispersive. So, the
localization error increases.
As a result, conventional cross-correlation fails to locate a leak when the waves
propagate in longer distance. The proposed method can still locate the leak and
the results show normal distribution behaviour despite of low precision by comparison with shorter distance. In such a word, the proposed algorithm has outstanding
performance in terms of distance range and positioning accuracy. Furthermore, it can
reduce the occurrence of false detection.
8.5 Conclusion
In conclusion, this work presents DTCWT with Soft Threshold De-noising method.
The signal is decomposed via DTCWT then soft threshold is applied to eliminate coefficients which smaller than the threshold. Thereafter, frequency-dependent
velocity is evaluated based on peak frequency from every level and used to locate
the water leak source, with time delay computed by cross-correlation. Experimental
results have verified that the proposed method has outstanding de-noising performance than wavelet de-noising by enhancing the signal features. In addition, it is
able to accentuate the cross-correlation peak. Thus, DTCWT-Soft Threshold Denoising is proven as an effective approach to reduce pipeline noise and locate leak
accurately by providing highest true detection rate.
Acknowledgements This research was financially supported by the Malaysian Ministry of Higher
Education (TRGS/1/2016/UTAR/01/2/3). The authors would like to acknowledge the support of
Universiti Tunku Abdul Rahman for providing the facilities.
References
1. SPAN, Water Services Industry Performance Report (Cyberjaya, Selangor, 2017)
2. O. Hunaidi, W. Chu, A. Wang, W. Guan, Detecting Leaks in Plastic Pipes. J. American Water
Works Association. 92(2), 82–94 (2000)
3. C. van den Berg, The Drivers of Non-Revenue Water: How Effective are Non-Revenue Water
Reduction Programs? World Bank Group (2014)
4. C. Liu, Y. Li, L. Fang, M. Xu, Experimental study on a de-noising system for gas and oil
pipelines based on an acoustic leak detection and location method. Int. J. Press. Vessels Pip.
151, 20–34 (2017)
5. J. Yang, Y. Wen, P. Li, X. Wang, Study on an Improved Acoustic Leak Detection Method for
Water Distribution Systems. Urban Water Journal. 10(2), 71–84 (2013)
6. S. Srirangarajan et al., Wavelet-based burst event detection and localization in water distribution
systems. J. Signal Process. Syst. 72(1), 1–16 (2012)
7. L. Meng, Y. Li, W. Wang, J. Fu, Experimental study on leak detection and location for gas
pipeline based on acoustic method. J. Loss Prev. Process Ind. 25(1), 90–102 (2012)
8. J. Wan, Y. Yu, Y. Wu, R. Feng, N. Yu, Hierarchical Leak Detection and Localization Method
in Natural Gas Pipeline Monitoring Sensor Networks. Sensors. 12(1), 189–214 (2012)
91
increases, the acoustic wave was attenuated and became more dispersive. So, the
localization error increases.
As a result, conventional cross-correlation fails to locate a leak when the waves
propagate in longer distance. The proposed method can still locate the leak and
the results show normal distribution behaviour despite of low precision by comparison with shorter distance. In such a word, the proposed algorithm has outstanding
performance in terms of distance range and positioning accuracy. Furthermore, it can
reduce the occurrence of false detection.
8.5 Conclusion
In conclusion, this work presents DTCWT with Soft Threshold De-noising method.
The signal is decomposed via DTCWT then soft threshold is applied to eliminate coefficients which smaller than the threshold. Thereafter, frequency-dependent
velocity is evaluated based on peak frequency from every level and used to locate
the water leak source, with time delay computed by cross-correlation. Experimental
results have verified that the proposed method has outstanding de-noising performance than wavelet de-noising by enhancing the signal features. In addition, it is
able to accentuate the cross-correlation peak. Thus, DTCWT-Soft Threshold Denoising is proven as an effective approach to reduce pipeline noise and locate leak
accurately by providing highest true detection rate.
Acknowledgements This research was financially supported by the Malaysian Ministry of Higher
Education (TRGS/1/2016/UTAR/01/2/3). The authors would like to acknowledge the support of
Universiti Tunku Abdul Rahman for providing the facilities.
References
1. SPAN, Water Services Industry Performance Report (Cyberjaya, Selangor, 2017)
2. O. Hunaidi, W. Chu, A. Wang, W. Guan, Detecting Leaks in Plastic Pipes. J. American Water
Works Association. 92(2), 82–94 (2000)
3. C. van den Berg, The Drivers of Non-Revenue Water: How Effective are Non-Revenue Water
Reduction Programs? World Bank Group (2014)
4. C. Liu, Y. Li, L. Fang, M. Xu, Experimental study on a de-noising system for gas and oil
pipelines based on an acoustic leak detection and location method. Int. J. Press. Vessels Pip.
151, 20–34 (2017)
5. J. Yang, Y. Wen, P. Li, X. Wang, Study on an Improved Acoustic Leak Detection Method for
Water Distribution Systems. Urban Water Journal. 10(2), 71–84 (2013)
6. S. Srirangarajan et al., Wavelet-based burst event detection and localization in water distribution
systems. J. Signal Process. Syst. 72(1), 1–16 (2012)
7. L. Meng, Y. Li, W. Wang, J. Fu, Experimental study on leak detection and location for gas
pipeline based on acoustic method. J. Loss Prev. Process Ind. 25(1), 90–102 (2012)
8. J. Wan, Y. Yu, Y. Wu, R. Feng, N. Yu, Hierarchical Leak Detection and Localization Method
in Natural Gas Pipeline Monitoring Sensor Networks. Sensors. 12(1), 189–214 (2012)