Izquierdo M A G, Hernández M G, Anaya J J, Martinez O
Departamento de Señales, Sistemas y Radiocomunicaciones, ETSI Telecomunicación, UPM, Ciudad Universitaria s/n, Arganda del Rey, Madrid 28040, Spain.
Ultrasonics. 2004 Apr;42(1-9):843-6. doi: 10.1016/j.ultras.2004.01.062.
Structural noise is a very important limitation to the visibility of flaw echoes in ultrasonic testing and evaluation of highly scattering materials. In order to enhance the signal-to-noise ratio, different algorithms have been developed. One of these techniques is based on filtering the spectrum low band of the received echo to obtain a significant improvement of the defect visibility. Based on this idea, in this work a new time-frequency technique is presented. In this method, block-processing autoregressive techniques are used to estimate the instantaneous center frequency of the traveling wave. From this information, a time-frequency filter is designed tuned at half the estimated instantaneous center frequency. Experimental results and the comparison with the non-time-frequency filtering technique are also included, showing that the proposed method has an excellent performance on SNR enhancement.
