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We study the causes complicating the application of the tone-burst method for the calibration of underwater vector sound receivers. We describe an experiment performed to confirm the correctness of the procedure of calibration of a vector receiver by the method of moving complex weighted averaging when the sensitivity measured in the reverberating sound field cannot be compared with the results of other independent methods. As a criterion, we use the correctness of measurements of the parameters of distortions introduced by the sound waves reflected from the water–air interface in the direct wave of the emitter. The proposed technique makes it possible to experimentally establish the possibility of selection of the vector quantity of the direct wave from the emitter in the reverberating sound field formed in the water tank within the frequency range overlapping the range of the tone-burst method and extended to the frequencies of the chamber of standing sound waves.

We present the results of comparison of national standards of the units of sound oscillation velocity of water particles within the range from 5 Hz to 10 kHz performed by the Hangzhou Applied Acoustics Research Institute (Pilot Laboratory) and the All-Russia Research Institute of Physicotechnical and Radio Measurements (VNIIFTRI) (COOMET 646/RU/14 Pilot Comparisons). The calibration capabilities of the participants were evaluated according to the results of measurements of the sensitivity of oscillation-velocity receivers: KGP-10, VHS56, and VHS90. At frequencies varying from 5 Hz to 500 Hz, inclusively, the calibrations were performed in a chamber as a result of comparison with a reference hydrophone performed by the method of oscillating water column. At frequencies higher than 500 Hz, we used the measuring procedure of the reciprocity method in the free field of traveling spherical sound waves. No significant inconsistencies in the calibration results were discovered at any frequency used for comparisons. The maximal discrepancies between the values of sensitivity obtained by the participants did not exceed 1.2 dB.

Problems arising from using the sensitivity of a hydrophone across a field to measure underwater noise are considered. Using the example of calibration of a hydroacoustic receiver, methods are shown for obtaining the energy and sectoral energy sensitivities of a receiver and the advantages of using them in measuring environmental noise and noise during certification tests of a vessel.

We present the characteristics of GET 55-2017, the State Primary Standard for reproduction and transmission of units of sound pressure and vibrational velocity in a water medium. We consider the operational principles of installations, measurement formulas and the results of the investigation of metrological characteristics.

A method and results are described for international interlaboratory comparisons of hydroacoustic measurement reference standards. The comparison was organized by the National Institute of Ocean Technology, India, with the participation of reference standards from Germany and Russia. Data are presented on the reference standard installations of the comparison participants and the measurement methods used, and the impact of water temperature on comparison results during calibration is discussed.

The characteristics of new measurement facilities which form part of the national special primary standard for reproduction and transfer of the unit of sound pressure in water media are described. The operating principles for these facilities and studies of related metrological characteristics are discussed.

Some new approaches for phase calibration of hydrophones by the reciprocity method are considered. Uses of this method for measuring the phase angle of the sensitivity for the geometric and acoustic centers of a hydrophone and for determining the position of the acoustic center from its shift relative to the geometric center of a hydrophone are described. Results from an experimental test of these techniques are presented.

Questions related to free-field calibration of hydrophones in continuous radiation of a bandpass signal in a reverberating water tank with the use of the cumulative moving weighted average method are considered. A broadening of the frequency range and a decrease in the calibration error are achieved by incorporating additional information on the behavior of the desired frequency dependence of the transfer impedance of the reflector-detector pair and with the use of multi-step averaging.

A special test facility is required for examining means of measurement under development in conditions corresponding to those of the environment where they will be used as regards chemical composition and thermohydraulic behavior, especially as regards the types and magnitudes of the external factors. A method is given for preparing certified aqueous mixtures under continuous flow conditions.