Experimental Verification of Acoustic Saturation

The maximum value of acoustic pressure within an ultrasonic beam is limited by acoustic saturation. The t oretical basis for acoustic saturation has been analyzed previously. In this work, a high-power pulse source is used to drive acoustic pressure levels from an ultrasonic beam to saturation. An automatic procedure determines the field’s beam axis using a calibrated Marconi PVDF hydrophone. The hydrophone measured RF waveforms are recorded along the beam axis and analyzed off-line. The peak compressional pressure is evaluated as a function of distance along the beam axis. The overall maximum pressure is compared to theoretical predictions. Three-, six-, and nine-MHz center frequency, 19-mm-diameter transducers were analyzed. The longer focal length transducer saturation level was comparable to a theoretical prediction. However, the theoretical saturation level for the shorte focal length transducers underestimated experimental results.