| 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 omega1 and omega2 to be close to resonant frequency omega0 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 omega1 and omega2 to form low-frequency wideband difference frequency Omega=omega1-omega2. Difference frequency Omega=omega1-omega2 is close to frequency Omegaos of resonant absorption of sound absorbed by bottom fish's swimming-bladder. High-frequency wave is irradiated additionally with frequency omega3 being close to resonant frequency omegaos of biological sound-dissipating layer which frequency interacts with wideband difference frequency wave Omega' reflected from gatherings of fish with swimming-bladder as well as with low-frequency wave of self-radiation of fish at frequency of Omega'' to form combination frequency waves of omega3± Omega' omega3± Omega''. After the procedure the signals with frequencies of omega3± Omega'and omega3± Omega''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 |
