A new point-source/point-receiver acoustic transducer for surface wave measurement

This paper presents the development of a new acoustic transducer for measur ing surface wave velocity using miniature conical PZT elements. The element s are directly fabricated out of a polarized PZT ceramic plate by excimer l aser micro-machining technique. The aperture size of the machined PZT conic al elements is around 200-400 mum in diameter, which allows high-frequency generation and detection of surface waves. Two of the transducers are assem bled together to form a transmitter/receiver pair. Driven by a tone-burst e lectrical system, the transmitter acts as an acoustic point-source which la unches surface acoustic waves propagating along a sample surface. The recei ver then detects the surface motion. The transfer function of the transmitt er/receiver system is experimentally determined. With a waveform. compariso n method, the surface wave velocities are obtained from the measured signal waveforms. Experimental results on several samples show that the surface w ave velocity can be determined accurately. Finally, the transducer is appli ed on anisotropic solids. The variation of surface wave velocity as a funct ion of propagation direction is determined. (C) 2001 Elsevier Science B.V. All rights reserved.