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Research Article

Academia Journal of Scientific Research 6(12): 486-493, December 2018
DOI: 10.15413/ajsr.2018.0153
ISSN: 2315-7712
©2018 Academia Publishing 




Use of the wavelet transforms for time of flight estimation of overlapping ultrasonic signals in thin coatings


Accepted 15th November, 2018

S. Laddada1,2*, S. Lemlikchi1 , M. O. Si-Chaib2 , H. Djelouah3 and A. Yahiaoui4

1Centre de Développement des Technologies Avancées, Baba-Hassen, 16303 Algérie.
2Solid Mechanics and Systems Laboratory (LMSS), University M'hamed Bougara Boumerdes, Algeria.
3Laboratoire de Physique des Matériaux, USTHB, Algérie.
4Laboratory of Dynamics Motors and Vibroacoustics 800Lgts boumerdes UMBB, Algeria.

Echoes detection and Time Of Flight (TOF) estimation is a challenging task in ultrasonic signal processing, especially in the case of overlapping echoes. Among existing methods, the wavelet transform method is the most used to process such signals. In this study, two methods based on the wavelet transform were investigated in order to yield the most accurate estimation of the TOF of overlapping echoes. The first one is the continuous wavelet transform based on Scale-Averaged Power (SAP), while the second method is the Discrete Stationary Wavelet Transform (DSWT). Both methods were applied for simulating Gaussian signals for two cases: partially and closely spaced overlapping echoes. To select a suitable mother wavelet, as well as the decomposition level for each method, several numerical tests have been carried out on the simulated signals. The performance was evaluated using the Mean Square Error (MSE) between the estimated value of the TOF and the actual value. Simulation results showed that both methods estimate the TOF with a reasonable error for the case of partially overlapping echoes. In the case of closely spaced overlapping echoes, the accuracy and the limit of the wavelet transform methods were obtained. Experimental validation was performed on real signals taken from thermally coated samples. A remarkable agreement was observed between simulations and experiments.

Key words: Time of flight, ultrasonic signals, overlapping echoes, SAP, DSWT, Thin coating.

This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Cite this article as:
Laddada S, Lemlikchi S, Si-Chaib MO, Djelouah H, Yahiaoui A (2018). Use of the wavelet transforms for time of flight estimation of overlapping ultrasonic signals in thin coatings. Acad. J. Sci. Res. 6(12): 486-493.

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