Study On Acoustic Characteristics Of Low Frequency Broadband Ventilation Muffler Based On Rough Neck Helmholtz Resonator

With the improvement of science and technology,noise pollution becomes more and more serious in our daily life.Due to the long wavelength of low-frequency noise,strong penetration and not easy to dissipate,it is difficult to achieve effective absorption with traditional sound absorbing materials.As a kind of classical acoustic device,Helmholtz resonator is widely used in noise control engineering to effectively reduce the noise of specific frequency because of its simple structure,easy processing,acoustic performance is not constrained by materials and easy to control,and has good sound absorption performance.In this paper,based on the sound absorption mechanism of Helmholtz resonator,by introducing the surface roughness into the neck tube of Helmholtz resonator,a low-frequency broadband ventilation Muffler based on the Helmholtz resonator with rough neck is designed.By adjusting the acoustic impedance of the structure to improve its low-frequency acoustic absorption performance,the specific research content is as follows:First of all,by using the combination of theoretical analysis and finite element simulation,the surface roughness is introduced into the neck of Helmholtz resonator to construct the sound absorption structure of rough neck Helmholtz resonator.to explore the influence of different structural parameters on the sound absorption performance of rough neck Helmholtz resonator,and optimize the rough neck Helmholtz resonator based on this.It is proved by experiments that after the introduction of surface roughness,the resonance frequency of rough neck Helmholtz resonator is reduced from 70 Hz to 58Hz(about 17.1%),and the sound absorption coefficient is increased from 0.68 to 0.76(about 11.6%).The improvement of lowfrequency sound absorption effect benefits from the acoustic impedance adjustment caused by the introduction of neck roughness,which also confirms the excellent lowfrequency sound absorption performance of rough neck Helmholtz resonator.Secondly,considering the condition of ventilation,we design a muffler with excellent low frequency sound absorption performance and broadband sound absorption.The influence of ventilation area on sound absorption performance is explored,and based on this,a low frequency broadband ventilation muffler sound absorption unit based on Helmholtz resonator is designed.By combining 8 sound absorption units with different expected resonant frequencies,the designed low frequency broadband ventilation muffler can achieve a sound absorption coefficient of more than 0.8 within the range of 500～1100Hz.On this basis,the surface roughness is introduced into the structure to optimize the low frequency broadband ventilation muffler.The optimized low-frequency broadband ventilation muffler,which is composed of 8 sound absorption units,can achieve sound absorption coefficient above0.8 in the range of 400～1200Hz under the condition that the volume remains unchanged,thus achieving the expected sound absorption target of low-frequency broadband ventilation.It can be seen that the designed low-frequency broadband ventilation muffler based on the Helmholtz resonator with rough neck has excellent low-frequency broadband sound absorption characteristics under ventilation conditions,which reflects the great potential in the field of noise control.