METHOD OF DETECTING AND IDENTIFYING BOTTOM FISH BY MEANS OF RESONANT ABSORPTION OF UNDERWATER ACOUSTIC SIGNALS RECEIVED BY FISH SWIMMING-BLADDER

摘要

FIELD: underwater acoustics.;SUBSTANCE: method can be used in fishing industry for detecting and identifying (species, quantitative and dimensional) of gathering of marketing bottom fish with swimming-bladder. Method consists in radiation of high-frequency pumping wave at the direction of bottom which waves have frequencies ω₁ and ω₂ to be close to resonant frequency ω₀ of air bubbles being present at subsurface layer of water at the direction of bottom. In non-uniform water medium high-frequency pumping waves exhibit non-linear interaction at frequencies of ω₁ and ω₂ to form low-frequency wideband difference frequency Ω=ω₁-ω₂. Difference frequency Ω=ω₁-ω₂ is close to frequency Ω_os of resonant absorption of sound absorbed by bottom fish's swimming-bladder. High-frequency wave is irradiated additionally with frequency ω₃ being close to resonant frequency ω_os of biological sound-dissipating layer which frequency interacts with wideband difference frequency wave Ω' reflected from gatherings of fish with swimming-bladder as well as with low-frequency wave of self-radiation of fish at frequency of Ω'' to form combination frequency waves of ω₃±Ω' ω₃±Ω''. After the procedure the signals with frequencies of ω₃±Ω'and ω₃±Ω''are received, detected and processed. According to the results of processing the decision of detection of marketing gathering of bottom fish with swimming-bladder at complex ground background is made and species, quantitative and dimensional characteristics of gathering are determined.;EFFECT: improved precision; increased reliability.;4 dwg