METHOD OF ESTIMATING NUMBER OF PROPELLER BLADES OF NOISY OBJECT AT SEA Russian patent published in 2016 - IPC G01S3/80 

FIELD: acoustics.

SUBSTANCE: invention relates to hydroacoustics and is intended for identification of sea vessels by their noise emission. Main point: noise signal spectrum of some sea vessel is analysed. In analysed signal spectrum, harmonic frequency of maximum amplitude is found and suggest it as primary frequency of blade sound row. N reference spectra are formed for N hypotheses on number of propeller screw blades. For each reference spectrum its similarity measure with spectrum of analysed signal is calculated. Diagram in polar coordinates is plotted for function depending of hypotheses on number of blades and measures of similarity for each hypothesis. Conclusion is made on number of blades in case resulting shape is similar to contour of screw with certain number of blades.

EFFECT: technical result is detection of information in observed signal spectrum, which can characterise number of screw blades, and visual, intuitive displaying of said information invariantly to object speed.

2 cl, 3 dwg