2014 Volume 55 Issue 7 Pages 1030-1033
An absolute hydrophone calibration technique using ultrasonic far-field with optical interferometry was extended to 40 MHz to evaluate the sound pressure amplitude generated by medical ultrasound equipment. A 1-mm nominal radius plane transducer was the calibration sound source for an ultrasonic far-field at 50 mm propagation distance at 40 MHz. The transducer’s effective radius was 0.88 mm at 40 MHz, with a range of 10–40 MHz. A coplanar membrane hydrophone with a 0.2 mm radius active element was calibrated using the technique at frequencies of 10–40 MHz with a 1 MHz frequency interval. Calibration results obtained using the developed system were compared with those obtained using our current calibration system. The discrepancy between those results was within the uncertainty of our current calibration system for frequencies of 10–20 MHz.