Research On Key Technologies For Active Control Of Line Spectrum Of Underwater Target Radiated Noise

In recent years,the acoustic stealth performance of underwater targets such as submarines and underwater vehicles has received increasing attention.Active control of underwater target radiation sound field is a key technology to improve acoustic stealth performance.Therefore,this article focuses on the three key links in the active control technology of underwater target radiation sound field.The three key links mainly include: modeling the acoustic field characteristics of underwater primary source radiation,designing the spatiotemporal and frequency domain of secondary parameter acoustic emission,and adaptive feature extraction and tracking methods for underwater signals.Main research content and work.Ⅰ.The equivalent source method and the unit radiation superposition method,as classic underwater sound field prediction methods,have their respective advantages,but the applicability of the low-frequency line spectrum active control system for underwater radiation sound field is still unclear.Therefore,the acoustic field characteristics of underwater primary source radiation were established based on the equivalent source method and the unit radiation superposition method.In terms of stability and speed,the sound field prediction is mainly based on the surface information of the shell,namely the vibration velocity characteristics of the shell surface,providing a theoretical basis for the design of sub parametric acoustic emission in the low-frequency line spectrum active control system of underwater radiation sound field.Ⅱ.Compared to conventional arrays,parametric arrays have advantages such as high directionality,small size,and the ability to generate low-frequency differential waves.Therefore,in terms of spatial domain,parametric sound field spatial design was conducted based on the KZK equation and three beamforming methods were demonstrated;In terms of time domain,the signal waveform was designed based on Berktay’s far-field solution and timedomain modulation method,and the influence of relevant parameters was discussed.Finally,the problem of beam deflection was solved through a phased parametric array,and the effects of array parameters on spatial directionality and spatial stitching were simulated.Therefore,in this technology,it has been proven that the square root modulation method is suitable for the low-frequency line spectrum active control system of underwater radiation sound field,and the phased beamforming method can provide a certain gain in the spatial domain,achieving good sidelobe suppression effect.Ⅲ.In terms of signal feature extraction and adaptive tracking,the classic Fx-LMS algorithm and Notch adaptive filter structure have their respective advantages.The Fx-LMS algorithm is widely used and can be applied to narrowband and broadband signals,while Notch adaptive filters are only applicable to narrowband signals.Based on the real-time and stability requirements of the low-frequency line spectrum active control system for underwater radiation sound field,theoretical research was conducted on the above two algorithms.Without considering the complexity of the algorithms,the convergence speed of weight values was explored,and noise resistance performance tests were conducted at different spectral levels of signal-to-noise ratios.The research results indicate that under a certain signal-to-noise ratio,the Notch structure has a faster convergence speed than the Fx-LMS algorithm in terms of convergence speed;In terms of anti noise performance,Notch’s tracking performance is slightly worse than the Fx-LMS algorithm at a signal-to-noise ratio of less than 15 d B.However,Notch’s tracking performance is better at signal-to-noise ratios greater than 15 d B,making it more suitable for active control systems of low-frequency line spectra in underwater radiation sound fields.Finally,the system transfer function of the low-frequency line spectrum active control system for underwater radiated sound field was derived,and the spatiotemporal control effect of the underwater target sound field was given through simulation.