The sound velocity is measured in distilled water in the pressure range 0.1-60 MPa and in the temperature range 0--40~ The results are given in the form of tables and an equation derived by least-squares processing of the experimental data.The behavior of the sound velocity in distilled water as a function of the temperature at atmospheric pressure is known within precise limits [I, 2]. In the underwater acoustics temperature range 0--40~ the Del Grosso algorithm [1], which is accepted worldwide in practice, coincides with the Russian State System of Standard Reference Data GSSSD 1117-18 algorithm [2] within the limits of a few millimeters per second.An analysis of the literature [2][3][4][5][6] shows that reliable data on the sound velocity in distilled water in the underwater acoustics pressure range 0-60 MPa are all but nonexistent. This void is a major obstacle to work on the metrological certification of sound velocity instruments. As a consequence, efforts to compile tables of the sound velocity in distilled water in the underwater acoustics pressure range 0--60 MPa must be directed primarily toward the acquisition of highly accurate data on the variation of the sound velocity in distilled water as the pressure is varied in the temperature range 0--40~ Measurements in the indicated range have been performed in the underwater test facility at the All-Russian Institute of Physicotechnical and Radio Engineering Measurements (VNIIFTRI) on the UVT-90-A-96 apparatus for reproduction of the sound velocity unit in a liquid and transfer of its dimension to standards of the lowest precision classes and working instruments [7]. The apparatus reproduces the unit in the velocity range 1000-2000 m/s, the temperature range 0-50~ and the hydrostatic pressure range 0.1-60 MPa in distilled water and in aqueous media with salinities up to 40 ppt.One of the main advantages of the method developed here and the apparatus used to implement it [7, 8] for the measurement of sound velocity in liquids is that the piezoelectric transducers are stationed outside the high-pressure chamber. This feature completely eliminates systematic error sources associated with the influence of pressure on the transducer characteristics, fluctuation of the acoustic bond between the transducers and the tubular metal waveguide used in other apparatuses, etc. The indicated systematic error sources tend to alter the phase shift in reflection of an ultrasonic pulse from the transducers, and the resulting change is difficult to take into account; these sources also change the acoustic path of the pulse (the effective distance between transducers) and other characteristics. It is important to note that the new method also completely eliminates the systematic error source associated with the so-called "wave effect" i.e., the dependence of the velocity of sound propagation on the ratio of the inside diameter of the acoustic waveguide (tube) to the ultrasonic wavelength when this ratio is large. The influence of the temperature measurement error on the error...

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