Research And Design Of Muffler With Multi-Stage Resonance Unit

Using artificial structures to manipulate sound waves is a frontier topic in condensed matter physics.The appearance of acoustic artificial structure provides a new research direction for the development of acoustic field.The application of new artificial acoustic resonance structure in sound absorption,noise reduction and other engineering problems is the research hotspot of applied acoustics.In this paper,a multi cavity reactive muffler composed of second-order Helmholtz element coupling is studied and designed.The noise reduction effect of the muffler can achieve a lower frequency noise reduction than that of the classical resonator under the condition of the same size resonator;Moreover,by coupling multiple second-order resonators,the resonance frequency of noise reduction can achieve continuous broadband noise reduction effect.In addition,based on the research of traditional Helmholtz resonators,combined with the resonance sound absorption and noise reduction theory of perforated plate with cavity and membrane with cavity,an acoustic super structure of perforated membrane with cavity is derived and designed,which achieves the sound absorption and noise reduction effect of wider frequency band than membrane resonance and lower frequency band than the common vibration frequency of perforated plate.The above results provide some theoretical guidance for the research and design of reactive muffler.The first part is based on the traditional Helmholtz resonator acoustics theory research,based on the equivalent circuit,the equivalent mechanics and transfer matrix method for second order cavity structure through theoretical derivation,the structure of the system impedance at high frequency formula,and through the structure is derived in every detail and part of the impedance correction parameters,the establishment of a more accurate numerical model,It provides a better theoretical support for the design of several second-order Helmholtz resonator coupled mufflers.In the second part,the acoustic advantages of the structure of the second order resonant cavity are analyzed by using the control variable method to change the geometrical parameters of the structure,and the variation law of the resonant frequency of the second order resonant cavity is summarized.The adjustment method of the formant bandwidth is obtained and verified.In this study,two resonators with similar operating frequencies were simulated by finite element method with different arrangement modes to obtain the effect of different arrangement modes on acoustic performance.Through the summary of the above theories and empirical rules as the theoretical support,a muffler is designed,which can achieve a continuous superior muffler effect in a wide resonance frequency band;Finally,the acoustic performance of the muffler is measured experimentally.Combined with the simulation calculation data,it is verified that the muffler designed in this paper has high matching and high feasibility.It has a wide application prospect in noise control engineering.In the third part,based on the study of the acoustic theory of traditional Helmholtz resonator,this paper combined with the resonant sound absorption and noise reduction theory of perforated plate and back cavity and membrane and back cavity,and derived a perforated membrane and back cavity acoustic superstructure was designed.The sound absorption and noise reduction effect is achieved with a wider frequency band than the membrane resonance band and a lower frequency than the perforated plate resonance frequency band.In this study,the feasibility and accuracy of the superstructure of perforated film and back cavity were verified by simulation and experiment.The research has a certain scientific significance in the application of noise absorption and reduction.