Noise Reduction In Enclosure Based On Adaptive Helmholtz Resonator

The noise of enclosed cavity such as ship cabins and aircraft cabins is widespread,which has become the research hotspot of scholars at home and abroad.The noise of ship cabin will lead to many problems,such as the reduction of ship vitality,the decline of concealment of warship,and the pollution of crew working environment.In recent years,relevant standards and regulations on the control and limitation of ship noise and emission have been issued.Traditional Helmholtz resonators are often used as low-frequency absorption units because of their simple structure and obvious low-frequency effect.However,there are some problems such as poor adaptability and narrow control band.Through the adaptive adjustment of Helmholtz resonator,the excitation frequency can be tracked.The spatial noise can be controlled and the control frequency band can be widened.Therefore,it is of great theoretical significance and engineering value to carry out the research of the noise reduction in enclosure based on adaptive Helmholtz resonators.The main work of this paper is listed as follows:The acoustic characteristics of Helmholtz resonator and sound field in enclosed cavity are studied.In order to solve the problem that the first derivative of sound pressure function on the wall is discontinuous to the space coordinate,the sound pressure function is expressed by three-dimensional improved Fourier series.The Helmholtz resonator is introduced into the enclosed cavity in the form of impedance.Lagrange energy method is used to describe the coupled model of the enclosed cavity and Helmholtz resonator.Combined with Rayleigh-Ritz method,the complete characteristic equation of coupled system is obtained,and then the acoustic modal characteristics of the coupled system are obtained.The sound field characteristics of a rectangular enclosed cavity are simulated.In free state,the natural frequency and sound pressure distribution regular pattern of the enclosed cavity solved by energy method are consistent with the analytical solution,and under the excitation of sound source,the sound pressure response curve at the observation point obtained by the energy method is consistent with the analytical solution,which verify the correctness of the method.The influence of Helmholtz resonator on the sound field in an enclosed cavity is further studied,and the feasibility is proved.In order to overcome the limitations of traditional Helmholtz resonators,this paper studies the adaptive Helmholtz resonators,and selects the point product method as the basic control algorithm.Under the condition of single frequency excitation,sudden change of excitation and bandwidth excitation,the point product method is simulated.The accuracy and stability of the algorithm are verified.In order to study the noise reduction of enclosed cavity efficiently and conveniently,the control algorithm program block diagram is designed and built based on Lab VIEW software platform,and the interface development of adaptive Helmholtz noise reduction system is completed,which effectively improves the human-computer interaction of the control process and shortens the development cycle.An adaptive Helmholtz resonator is designed to realize the frequency modulation process by changing the area of the resonator neck.The correctness and stability of the proposed method are further verified by experiments.The results show that the adaptive Helmholtz resonator designed in this paper has great effect on the noise reduction of the enclosed cavity.In addition,the Lab VIEW control interface is simple,intuitive and easy to operate.