Using the methods of boundary integral equations, the radiating object's field within the closed water area is defined. A Green's function for the closed water area with different boundary impedances is built. The sound-pressure field around the object is calculated on the basis of predicted (already measured) discrete pressure levels on the object's surface that is irritated by the a priori unknown inner vibration sources of various nature. The algorithm of computation is used to find out the potentials of a single (or double) layer at the separate points (spots) on the object surface on the basis of sound-pressure amplitude and relative phase measurements in these very points. The experimental data within the frequency range of 2--256 Hz corresponded well enough to the suggested theoretical model of the problem. The differences between calculated pressure amplitudes and measured ones did not exceed the value of 6 dB. The 128-channel phase measurements have been run within the narrow frequency band after the signals' time processing. The phase shift at the separate points has been defined with respect to the reference hydrophone located at the bow side of the object. The methods of noisy object's sound field prediction (recomputation) from the closed water area measurements to the open sea deep water waveguides' conditions are suggested. The methods are based upon the modified reciprocity principle.