Abstract--We consider specific errors of measuring the velocity of sound in water caused by the effect of heating of the analyzed volume of the medium by acoustic irradiation and the influence of the velocity of the incident flow. We deduce expressions for the optimal values of the intensity of sounding acoustic radiation and the velocity of the incident flow guaranteeing the minimum possible value of the resulting error and give recommendations concerning the in situ measurements of the sound velocity.The determination of the parameters of the thermodynamic state of marine media according to the data of direct measurements of the sound velocity C and some other hydrophysical parameters requires the attainment of the maximum possible accuracy of measurements [1]. Since the corresponding equations of state of seawater contain the local velocity of propagation of low-amplitude sound in a nonperturbed immobile medium and, in the in situ measurements, the instrument always moves relative to the medium, it is necessary to estimate the influence of the velocity of this motion (scanning) on the results of measuring C. In addition, a gauge of sound velocity C is a parametric primary measuring transducer radiating energy that dissipates into heat in the effective volume of the gauge, which perturbs the state of the investigated medium and, hence, distorts the field of sound velocity. Therefore, in the evaluation the resulting measurement error of the sound velocity, it is necessary to take into account these two basic effects of interaction of the sound-velocity meter (SVM) with the investigated marine medium. The evaluation of specific effects of heating and the flow velocity on the results of measuring C was made in [1]. It was shown that these effects are significant. Later, the analysis of the effect of heating of the medium was carried out in [2] but without taking into account the flow velocity. In the present work, within the framework of the model of linear acoustics, we study the influence of the intensity of sounding acoustic radiation P and the velocity V of the incident flow on the resulting error e of measuring C and demonstrate the possibility of minimization of E by the optimal choice of the quantities P and V.We determine the error e as the relative deviation of the measured value of the sound velocity C from its true (actual) value C:e= C-c= A__C_C C C' * Translated by Peter V. Malyshev and Dmitry V. Malyshev UDC 534.22
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