Structural Design And Acoustic Performance Study Of Membrane Muffler

Muffler is a common device for noise control of power machinery.Traditional hindrance mufflers are generally used to eliminate middle and high frequency noise,while the cross section or cavity resonance anti muffler is generally used to suppress the propagation of low frequency noise,but a reactive muffler will increase the pressure loss.Unlike the reactive muffler,membrane muffler introduces the film into the muffler,and uses the flexible structure and acoustic wave coupling to achieve the purpose of low frequency noise reduction,reducing the pressure loss in the muffler.However,in the actual noise environment,the frequency often changes.It is of theoretical significance and practical value to study the membrane muffler with FM function.On the basis of the analysis of the principle of the muffler,the Green function and the Kirchhoff-Helmholtz integral are used to calculate the radiative field and the transmission loss of the membrane muffler,which provides the basis for the design of the membrane muffler.Secondly,the structure of membrane muffler is designed,and the effect of film material,shape and back cavity on noise reduction effect of membrane muffler is studied.The results show that the loss of sound frequency and transmission loss can be widened by selecting the thin film with small stiffness,and the transfer loss of the circular film is 10 dB higher than that of the rectangular film,and the number of the peak value of the transfer loss is also increased.In order to widen the noise elimination band of the film muffler,the experiment of adding different mass blocks on the film,adding holes on the film and changing the number of holes on the film and changing the pre-stress on the film are designed to reduce the fixed frequency noise.Finally,two adaptive control schemes of membrane muffler are designed.By changing the height of the back cavity of the membrane muffler,the resonance frequency of the membrane muffler will be shifted.When the height of the back chamber is increased from 30 mm to 130 mm,the resonant frequency of the membrane muffler is shifted to 440 Hz.By changing the voltage at the two ends of the piezoelectric chip,the stress of the film is changed,and the resonance frequency of the membrane muffler is shifted.When the voltage at the two ends of the piezoelectric chip rises from 0V to 400 V,the resonant frequency of the membrane muffler is offset by 45 Hz.The research results show that the designed membrane muffler with adaptive adjustment function can automatically adjust the voltage of the piezoelectric vibrator at both ends of the piezoelectric vibrator from the change of the noise source frequency in 455 Hz to 500 Hz,and change the noise elimination frequency of the membrane muffler,and complete the autonomous control of the noise.