Adaptive Control Method Of Underwater Low Frequency Noise Based On Normal Energy Flow

The low frequency radiated noise of underwater vehicles is not only the key feature that makes them exposed,but also causes noise pollution to the marine environment.After years of development,passive noise control technology can reduce the radiated noise of underwater vehicles to a certain level,but it is still difficult to suppress the leakage of low frequency line spectrum nosie of underwater structures.Therefore,people turn their attention to active noise control technology,which uses the principle of acoustic interference cancellation to control low frequency noise.In general active noise control methods,the sum of the squares of sound pressure at one or more points in the sound field is selected as the control target.The main implementation is local noise reduction,the radiated sound power of the system may not be able to reduce,Sometimes it may even increase.In addition,for complex underwater structures,when the frequency changes,the distribution characteristics of the radiated sound field will also change greatly.When the sound pressure is used as the error signal,the layout of secondary sound source and error sensor are often different,resulting in poor versatility of the active noise control system in different environments.In order to further realize the noise reduction in the whole space or designated local area,it is necessary to optimize the number and layout position of secondary sound sources and error sensors for different working frequency bands.Aiming at the of low frequency radiated noise control problem of underwater vehicle,the theoretical research and numerical analysis of underwater low frequency adaptive noise control method based on normal energy flow are carried out,proposes an adaptive control algorithm based on double hydrophone method,and develops an adaptive controller.The normal sound energy flow is a vector and represents the propagation direction of energy.In principle,controlling the normal sound energy flow in the near field can reduce the sound energy in this direction.In this paper,the sound field characteristics of the combined pulsating sphere source are analyzed by numerical analysis method,and then the optimal configuration of the secondary sound source and error sensor is carried out,and the active control effects of radiated noise of underwater structures based on sound pressure and normal sound energy flow are compared.Secondly,the active noise control technology is used to suppress the low frequency radiated sound field of underwater ribbed cylindrical shell filled with water.When the sound pressure and normal sound energy flow are used as the control targets respectively,the control effects of different secondary sound sources combinations on the radiated noise of underwater structures are studied.Finally,the simulation analysis of radiated noise control effect and the principle verification test of active control method are carried out by using a single-layer cylindrical shell.The simulation and experimental results both show that the active control method based on the normal acoustic energy flow can be applied to the low frequency noise control of underwater structures.