Results of Pilot Comparisons of Amplitude–Phase Calibrations of Hydrophones in the Frequency Range 10–500 kHz COOMET 786/RU-a/19

Initiated by COOMET TC 1.2 "Acoustics, Ultrasound, Vibration," bilateral pilot comparisons of amplitude– phase calibrations of hydrophones in the frequency range 10–500 kHz COOMET 786/RU-a/19 between the Hangzhou Research Institute of Applied Acoustics (HAARI) and the Russian Metrological Institute of Technical Physics and Radio Engineering (pilot laboratory) are described. Characteristics of reference hydrophones, data on standard facilities and calibration methods, results of calibrations, and assessments of reference levels of comparisons are provided. The results of comparisons are discussed. The problems that influenced the results of comparisons are mentioned. The correctness of the measurement methods used by the participants of the comparisons, including the method of calculating the frequency dependence of the argument of hydrophone complex sensitivity on the experimental frequency dependence of the modulus of its sensitivity, has been confirmed. The results of the pilot comparisons were found to be satisfactory. When discussing the results of comparisons at the COOMET TC 1.2 meeting, it was proposed to conduct additional comparisons of the results of amplitude–phase calibrations in an expanded composition of participants. The results obtained allow verifying the correctness of the adopted new technical solutions, working out methods for performing measurements and post-processing of the data obtained, identifying and numerically assessing sources of uncertainty, and also establishing previously unaccounted sources of uncertainty when improving primary standards.