The smart concrete module embedded PZT seen as acoustic source is with ultrasonic detection function.Model analysis of PZT wafer shows different maximum multitude distribution on the wafer acoustic radiating surface.The experiment based on smart concrete module shows while the radiating surface seen as superposition of equal multitude single point source and ignoring the vibration mode

the acoustic directivity variation deviates from the actual with frequency

and the directivity becomes divergent at a frequency.The first natural frequency is more suitable for ultrasonic detection considering the acoustic directivity and energy.