Research On Simulation And Experiment For Acoustic Performance Of Silencer

Transmission loss of the silencer,which is subject to the geometry of the silencer,is an important acoustic indicator in related theoretical research.Due to the difference in acoustic impedance,the acoustic performance of an water-filled silencer is different from an air-filled one,even with the same geometry.Thus,the difference of transmission loss between water-filled silencer and air-filled one is investigated in simulation based on COMSOL and experiment in this paper.In order to increase the reliability of the experimental results,measurement of speed of sound is also carried out in this paper.First,previous research on transmission loss' s calculation and experiment is summarized.Then,especially,the physical meanings and measurement method of four pole-parameters of transfer matrix are also introduced emphatically.The transmission loss of water-filled silencer considering acoustic-structure interaction is calculated by COMSOL,and the result is compared with that rigid wall.From comparison,it is proved that the acoustic-structure coupling effect on the acoustic performance of the water silenceris is innegligible.The effect of shell thickness,gas content and distribution on the acoustic performance of water silencer was also analyzed.This paper introduces the basic principle and data processing of the three-sensor method to measure the sound speed of pipeline in the experimental part.And the sound speeds in the air-filled and water-filled pipes are measured.The measurement result is in accordance with the expectation,which validates the experimental setup and provides a reliable sound speed for the transmission loss measurement.The detailed principle of wave decomposition method,two-source method and two-load method is given,and the relevant formula is derived.The above methods were used to measure the transmission loss of air-filled silencer and water-filled silencer.The results of different measurement methods agreed with each other,and the validity of the measurement was verified.The relationship between the working frequency and the distance between the measuring points is illustrated by theory and experiment.The effect of gas content on the transmission loss of water silencer is analyzed in experiment,and the same comclusion is made in simulation.With the increase of gas content,the curve of transmission loss in low-frequency region tends towards lower frequencies whilethose in middle and high frequency region shift to higher frequencies.