Magnitude and phase reciprocity calibration of ultrasonic piezoelectric   disk in air
  A modified conventional three-transducer reciprocity calibration method is used to measure the magnitude and phase responses of the transmitting voltage response and the free-field open-circuit receiving voltage sensitivity of ultrasonic piezoelectric transducers radiating in air at 1 atm. The transducers used in this work are 20 x 2 mm circular piezoelectric ceramic disks with their first and second radial modes at approximately 100 and 250 kHz, respectively. The transducer characterization is supported and aided by finite element simulations of the measurement system and the measured frequency responses. Preliminary results indicate that the magnitude and phase responses of the transmitting voltage response and the free-field open-circuit receiving voltage sensitivity can be measured with fair accuracy in a limited frequency band around the first radial mode of the piezoelectric ceramic disk. Further work is needed to demonstrate and quantify the accuracy actually obtained using the three-transducer reciprocity calibration method, to achieve transducer characterization at a calibration accuracy level, and to achieve calibration above the calibrated frequency range of the B&K 4138 microphone. 
Kenneth K. Andersen, Per Lunde, Jan Kocbach
physics.ins-det