Extraction And Analysis Of Acoustic Impedance Of Perforated Plates Of Perforated Silencers

The muffler is widely used in various piping systems due to its good noise reduction performance.Therefore,the perforated pipe and the perforated plate are important components in the muffler and related research work has also received great attention.Acoustic impedance of the perforation is an extremely important parameter in the calculation of the acoustic performance of the perforated muffler.The sound propagates through the small hole through the pipe which will cause the change of the acoustic impedance of the perforation and it can also affect the acoustic performance of the muffler.Since the acoustic impedance model of perforation in water pipeline has not been published yet and the density of water medium is big,it is easy to form an acoustic-solid coupling effect with the wall of the muffler when the sound propagates in the water medium.Therefore,multi-physics should be used in the water pipeline muffler.We can use the coupling software of COMSOL to establish a finite element model of thermal viscous or acoustic-solid coupling in order to investigate the influence of the attenuation of acoustic waves in the medium on the acoustic impedance of the perforation considering the thermal viscous and acoustic-solid coupling effects.Then we can determine the simulation model that can accurately calculate the acoustic impedance of the perforation.Based on the orthogonal experiment,we analyze the influence of different structural parameters of water pipe perforated plate on acoustic impedance in detail and the acoustic impedance model of water pipe perforation is obtained by multivariate nonlinear regression analysis.Based on the acoustic impedance model of water pipe perforation obtained in this paper,we can calculate the transmission loss of the perforated pipe muffler in water pipeline and compare with the calculation results of three-dimensional time domain CFD method.The two calculation results are in good agreement and the water pipe perforation obtained in this paper is verified.The acoustic impedance model can well simulate the physical properties of small holes with good applicability and high accuracy.Furthermore,the influence of the structural parameters of the perforated plate on the acoustic performance transmission loss of the water line muffler is explored which provides some guidance for the engineering design of the muffler.In the air pipeline,it's rarely mentioned that the effects of thermal viscosity and acoustic-solid coupling on the acoustic impedance of perforations.In this paper,the finite element model of perforated acoustic impedance in air pipeline is established by the same method.The acoustic impedance of air tunnel perforation is extracted and the formula is fitted to obtain a new model of perforated acoustic impedance in air pipeline.The new acoustic impedance model of air pipe perforation obtained in this paper considers the hot viscous effect compared with the existing acoustic impedance model in the literature.The transmission loss of the perforated tube muffler in the air line is calculated by using the new model of perforated acoustic impedance and the acoustic impedance model existing in the literature and compared with the experimental measurements.The results show that the new model of air circuit perforation acoustic impedance obtained in this paper can more accurately simulate the physical properties of the perforated plate.