Research On Active Noise Insulation Of Water-filled Acoustic Cavity Based On Double-Layer Structure

Sonar self-sound is one of the main factors that affects the signal-to-sound ratio of sonar detection.Suppressing the transmission of sound excitation to the sound field in the sonar cabin is the key to maintaining the performance of the sonar.Sonar self-sound is mainly transmitted into the sonar cavity through the two paths of the dome and the inner wall of the sonar cabin,so it can be classified as ’outside sound’and ’hull sound’ according to the transmission path.About suppressing the self-sound transmission of sonar,current researchers have been focusing on applying various advanced methods,strategies,new technologies,and new materials to suppress’outside sound’ from being transmitted to the sonar cabin through the deflector.There were few studies on suppressing the transmission of hull sound through the bulkhead to the sound field in the sonar cabin,and most of the research directions focused on traditional passive sound insulation methods.The high frequency sound insulation effect is obvious,and the middle and low frequency sound insulation effect is poor.There has been some successful applications of active sound reduction in the filed of aerospace,and the current main structure of ship bulkheads is still a single-layer or double-layer steel plate with a ribbed structure,so the research of active sound insulation based on double-layer plate structure-water-filled acoustic cavity has important theoretical value and engineering significance.In this paper,we summarized the domestic and foreign research data on sonar chamber structure fluid-structure interaction,double-layer plate sound insulation,Semi-active/active control strategy,and elastic plate-acoustic cavity coupling etc.Then introduce the theory of active sound insulation control into the double-layer sandwich panel structure-sonar cavity fluid-structure interaction system and make a model,And analyze the influence of different control strategies and different influencing factors on the sound insulation characteristics of the system based on numerical calculation.This paper aims to initially explore a part of the active sound insulation control strategy,which can make the double-layer plate structure-water-filled acoustic cavity active sound insulation system suppress the transmission of the excitation energy of the mid-low frequency ’ship sound’ to the sound field in the sonar cavity,including feedback control strategies and equivalent Sky-hook damping control strategy.Starting from the second chapter,Based on the typical structure of the sonar cabin and the wave equation of the classical boundary conditions,a theoretical analysis model of the elastic plate structure-sonar cavity fluid-structure coupling system is established,and the complex mode and average energy input theory are introduced,we derived the FR(frequency response)calculation formula of the double-layer plate structure-acoustic cavity fluid-structure interaction system and the FR calculation method corresponding to the passive sound insulation method of the system.Chapter Three,based on the aforementioned theoretical model,we introduced the feedback control link and derived the theoretical analysis model of the double-layer plate structure-acoustic cavity fluid-structure interaction system and derive the time-domain calculation method of the average energy input of each main link on the energy transfer path of the system.Then,we use numerical calculation methods to analyze the changing law of the average energy transfer characteristics of the single-support/multi-support sandwich layer system when the feedback parameters continuously change,and then perfect the double-layer board structure-sonar feedback control sound insulation strategy.Results showed:When the six feedbacks parameters were located in their assigned assigned areas,each active control method with the feedback parameters can independently produce obvious low-frequency sound insulation effects.However,only the absolute acceleration feedback control method had obvious high-frequency sound insulation effects when the parameter is in the specified assignment area.Chapter Four,using the ideal Sky-hook damping control theory,we preliminarily discussed and analyzed the application of the equivalent Sky-hook damping control theory to 24 related control strategies for system sound insulation,and carried out theoretical analysis and modeling.Then Derive the time-domain calculation method of the average energy input of each main link on the energy transfer path of the system.Next we analyzed the effect of the changes of the aforementioned 24 control strategies and the change of the controllable damping value on the sound insulation performance of the system through numerical calculations,and finally 7 control strategies are retained.Then we used numerical calculations to analyze the influence of the change of controllable damping on the sound insulation effect of the remaining 7 control strategies.Finally based on practical considerations,a general method for quickly adjusting the acoustic characteristics of a double-layer board structure sound insulation system using simple comparison of numerical calculation results was proposed.