A Reciprocity-Based Method to Determine Hydrophone Complex Sensitivity and Tested at Frequencies from 1 to 7 MHz

Ultrasound hydrophone calibration comprises its sensitivity determination. Among different methods, the self-reciprocity one is absolute, traditional, long-time validated and standardized by International Electrotechnical Commission for calibration of hydrophone sensitivity magnitude. Self-reciprocity is the basis for the method in the present work, which uses an auxiliary transducer and a flat reflector immersed in a water tank and allows calculating the on-axis pressure waveform, given the excitation signal and the propagation medium properties. The pressure waveform at the hydrophone is calculated and used with the output-voltage waveform to determine its complex sensitivity. The method was tested at discrete frequencies from 1.0 to 7.0 MHz using two similar PVDF membrane hydrophones, previously calibrated in magnitude by NPL. The results are metrological acceptable, with inter-laboratorial agreement within the declared uncertainties in magnitude sensitivity (less than 11%) and intra-laboratorial agreement in sensitivity phase calibration, with uncertainty of less than 17 degrees.