Study On The Influence Factors Of The Absorption Coefficient Of Perforated Panel Resonant Sound Absorber Measured By Impedance Tube

Perforated panel resonant sound absorbers are advantageous at medium and low frequencies,with good fire resistance,corrosion resistance,and withstanding the impact of high-speed airflow,so they are widely used in noise control.The impedance tube method can be used to quickly measure the sound absorption coefficient,but in the measurement,if the specimen is installed in different ways,the test results will be biased.Therefore,in this paper the influence of specimen installation and experimental device on the test results in impedance tube test are analyzed by the theories,the numerical simulations and the experiments.Firstly,taking a Perforated panel resonant sound absorber as an example,sound absorption coefficients obtained by theory,four numerical simulation methods and impedance tube method are compared and analyzed.Secondly,the influence of the gap between the perforated plate and the tube wall,the inclined angle between the perforated plate and the tube wall,and the thickness of the impedance tube wall on the sound absorption coefficient were analyzed by simulation.Finally,the influence of different sealing materials on the test results of sound absorption coefficient is studied experimentally when there is a gap between the perforated plate and the impedance tube wall.The results show that: Compared with several different calculation models,the results of considering the viscous loss of perforated plate are closer to the actual value.When there is a gap between the perforated plate and the impedance tube,the first resonance frequency moves to high frequency,and the sound absorption coefficient increases gradually with the decrease of the gap.In normal installation,the oblique incidence of sound wave caused by the inclination angle of perforated plate is less than 2° and has little influence on the sound absorption test results.When the impedance tube wall is made of steel,the wall thickness of 3.4mm can meet the needs of low-frequency sound insulation.When there is dimensional error in the processing of perforated plate,it is better to use paper tape with silicone grease,silicone grease and silicone rubber for sealing.Considering the sealing effect and the convenience of operation,silicone grease or silicone rubber can be selected for the size deviation less than 0.3mm.For the test pieces with size deviation greater than 0.3mm,paper tape and silicone grease can be used for sealing or only silicone rubber can be used.