Calibration and Performance Evaluation of Miniature Ultrasonic Hydrophones Using Time Delay Spectrometry

Abstract

A novel calibration method suitable for performance evaluation of hydrophones for ultrasonic dosimetry in the frequency range between 1 and 10 MHz is described. The principal advantage of this method over conventional discrete frequency calibration is that it is able to detect rapid and significant variations in frequency response of the ultrasonic hydrophones due to e.g. spurious mechanical resonances. The method employs Time Delay Spectrometry (TDS) technique which not only facilitates assessment of the hydrophone free field parameters in reflective environments but also allows both frequency response and directivity patterns of the ultrasonic hydrophone probes to be determined as a continuous function of frequency. The advantages and limitations of the TDS technique are pointed out.