To measure the energy of the source of acoustic pulses in the absolute scale of units (J) from the registered pulses, an analysis of the energy balance "source of pulses" -- "transmitting medium" -- "receiver of pulses" was carried out using a spectral analysis device. Comparison of two independent methods for determining the energy of elastic interaction (capacitive method and photoelasticity method) gave a discrepancy between the results of less than 12%. The spectral composition of the interaction energy is determined. The results make it possible to determine both the parameters of the signal source and the structure of the transmitting average signal conversion. To measure stresses in an elastic wave, a piezoelectric receiver, in which a piezofilm served as a sensitive element. This receiver differs from receivers made on the basis of piezoceramic elements, has a significantly lower non-linearity of the amplitude-frequency characteristic, since it has only two natural frequencies. Keywords: photoelasticity, elastic wave velocity, rock mass, concrete, acoustic emission.