TECHNOLOGY OF PROTECTION OF UNDERWATER CRAFT AGAINST DETECTION BY SONAR Russian patent published in 2002 - IPC

FIELD: underwater acoustics. SUBSTANCE: technology of protection of underwater craft against detection by sonar consists in substance in irradiation of layers of liquid boundary on craft in points of location of dominating sources of noise making, predominantly in area of running mechanism of craft, with the use of ultrasonic radiation of medium ultrasonic range. It enables frequency range of primary and secondary hydroacoustic fields of craft to be transferred from infrasound and sound regions to ultrasonic region thanks to nonlinear interaction of waves. Waves are heavily absorbed by neighboring layers of water in region of medium ultrasonic range. Besides capsule with high-frequency hydrophone is towed by cable to check low-frequency component of noise propagating in stern direction of craft. After demodulation of ultrasonic signal information on level of noise on low frequencies in most probable direction of craft is sent to craft. EFFECT: possibility of reduction of level of primary and secondary fields of craft and provision for control over low-frequency component of noise making in direction of stern.