The results of researches of aposteriorny density of probability of an angular modulation index assessment of the heterodyne laser Doppler vibrometer (LDV) signal observed in mix with additive Gaussian noise are given in the report. Comparison of results of an analytical calculation of the distribution law of information parameter with results of numerical modeling of the oneloopback system of an optimum nonlinear filtration is carried out. The received results allow to formulate conditions under which the hypothesis of Gaussian model of aposteriorny distribution with a certain probability is fair.