METHOD FOR DETECTING AN UNDERWATER BROADBAND NOISE SOURCE Russian patent published in 2023 - IPC G01S3/80 

FIELD: hydroacoustics, in systems of noise direction finding and monitoring of the underwater environment, providing detection and localization of underwater vehicles by noise emission.

SUBSTANCE: in the oceanic environment, waveguide dispersion and multimode propagation of sound lead to the formation of a stable interference pattern (interferogram) of the noise field of the source. The configuration of localized interferogram bands is determined by the waveguide parameters, the speed and trajectory of the noise source. Holographic processing of the source noise field implements a quasi-coherent accumulation of spectral intensity along localized bands, to which a two-dimensional Fourier transform is then applied. The spectral density of the sound field is concentrated in a small region at the output of the integral transformation (hologram) in the form of focal spots caused by interference of modes of different numbers. The hologram records the amplitude-phase distribution of the interferogram during observation in the frequency range under consideration and contains information about the distance and radial velocity (velocity projection towards the receiving system) of the source. The accumulation of interference along the interferogram bands is incoherent, and the interference is distributed over the entire area of the hologram. A condition is accepted as a method for detecting a noise source under which the maximum of the angular distribution function of the spectral density of the hologram (detection function) is twice or more higher than the interference peaks. The angular distribution of the spectral density is defined as the sum of the spectral densities along the lines passing through the origin in the first and fourth quadrants of the hologram. The method for detecting the source does not require knowledge about the nature of the signal, interference and transfer function. The method involves the generation of interferograms of the received signal at the output of the receiving system via the VSP frequency channels covering the entire observed frequency range. For each frequency range, an interferogram is generated in the frequency-time variables of the received signal via the VSP channels. A hologram is recorded in the time-frequency variables. The detection functions are calculated from the generated holograms. A decision is made based on the analysis of the detection functions about detection of the source for each of the VSP frequency bands and channels.

EFFECT: present invention enables to increase the noise immunity of the receiving system using a single vector-scalar receiver (VSP) containing a sound pressure channel and three channels of the oscillatory velocity vector, and increase the detection range of the noise source based on holographic processing of the noise signal on the vector-scalar channels of the receiving system.

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