Free Field Reciprocity Calibration in a Convergent Spherical Acoustic Wave of a Focusing Transducer

Basis on the reciprocity theorem of acoustic field, we derive the formula of reciprocity coefficient of a convergent spherical acoustic wave and calculate a series of the diffraction corrective factor curve of reciprocity coefficient of transducers. Using these formulas and corrective factors, we calibrate the free field transmitting current response and the free field voltage sensitivity of a focusing transducer by the self-reciprocity method. Experimental results of reciprocity calibration of the focusing transducer in the frequency range of 2 MHz to 5.4 MHz are presented.