For efficient NDE of pipes, essential components of power plant facilities, ultrasonic
guided waves were generated and received applying an air-coupled transducer and comb one as
non-contact technology. Mode generation and selection were predicted based on theoretical
dispersive curve and the element space of a comb transducer. In addition, a receiving angle of the
air-coupled transducer was determined to acquire the predicted modes by theoretical phase velocity of
each mode. Theoretical dispersive curve was compared with the results of the time-frequency
spectroscopes based on the wavelet transform and 2D-FFT to identify the characteristics of the
received mode. The received modes show a good agreement with the predicted ones.
