Research On Active Control Method For Radiated Noise Of Underwater Structures Based On Normal Energy Flux

The low frequency acoustic target characteristic of underwater navigation target is the main source of its exposure.Effective control of its low frequency radiation acoustic field can improve its survivability,which is of great significance.There are mainly passive and active methods to reduce the radiated noise of underwater structures.Passive noise reduction has great limitations on the low frequency noise control,while active control methods can theoretically achieve low frequency and high-power noise reduction.Traditional active noise reduction mainly uses sound pressure information in the near field for active control.When controlling the noise of underwater structures,often the far-field radiation sound pressure is need to be controlled.Apparently,it is difficult to place the sensors in the far field.In addition,it is difficult to calculate the far-field sound pressure accurately,especially the phase information,based on the sound pressure test results in the near field.Therefore,using the traditional sound pressure information in the near field is hard to realize the sound pressure control in the far field.Aiming at this problem,this paper proposed an active control method for underwater structure radiation noise at low frequency based on normal acoustic energy flux.From the perspective of energy control,this method avoids the problem of obtaining far-field phase information,and uses near-field sound energy flux as the controlled physical quantity to realize effective noise reduction for far-field radiation sound field.Normal energy acoustic flux refers to the product of sound pressure and normal velocity.It is a function of time,and its time average is the normal sound intensity.The underwater structure radiated sound power can be obtained by integrating the sound intensity at the surface of the structure.Therefore,the reduction of the normal acoustic energy flux can result in a reduction of the radiated sound power,which in turn realizes the control of the far field radiated sound pressure.In this paper,the basic principles of the active control method based on normal energy flux for the radiation sound field at low frequency has been studied firstly.Then,the distribution characteristics of the radiation sound field at low frequency of the underwater combined pulsating ball sources and underwater structures have been numerical analyzed.Thirdly,the numerical simulation analysis of the two active control methods based on sound pressure and based on the normal energy flux are carried out respectively under different parameter condition.Moreover,the numerically simulation for the active noise control method proposed in this paper in the channel environment has been carried out to prove the feasibility.The numerical simulation results show that,compared to the traditional active control method based on sound pressure,the active control method based on normal energy flux has a significant effect on reducing the low frequency far-field radiation noise of underwater structures.