Transmission and reception of short ultrasonic pulses by circular and square transducers

Abstract

The transient fields of circular and square wide-band (1–5 MHz) ultrasonic transducers have been studied in water. Transmission and reception of short pulses have been observed using a small (150 μm) wide-band probe as both receiver and transmitter. Transmit-receive mode results from a small target have also been considered. Detailed comparisons with the theoretical waveforms for an ideal transducer (pistonlike in transmission and pressure-sensitive in reception) exhibit generally good agreement. The principle of reciprocity between transmission and reception has been verified. Discrepancies from pistonlike behavior, most marked at short ranges near the axis of each transducer, have been shown by schlieren observations to be caused by an extra (’’head’’) wave which originates from a plate wave propagating laterally across the face. It is concluded that nearfield pulse echo results must be interpreted with some circumspection.