Study On Relationship Of Material’s Absorption Coefficient Between Reverberation Chamber Method And Impedance Tube Method

Sound-absorbing materials can effectively reduce indoor noise and improve sound quality of halls. Important parameter to evaluate the performance of sound-absorbing material is the absorption coefficient of sound-absorption material. Experiment is the main way to get absorption coefficient of material. The main method to test the absorption coefficient is:reve-rberation chamber method and impedance tube method. The random-incidence absorption co-efficient of sound-absorbing materials αs can be measured by reverberation chamber method. Since the sound field of the reverberation chamber is diffuse sound field which is closer to reality. The normal-incidence absorption coefficient of sound-absorbing materials α0can be measured by impedance tube method. Since small sample is needed, so it is simple to make, helps to reduce the cost of experiments and facilitate research. But when the reverberation time of the material is measured in reberberation chamber, a standard sample of the material to be tested, must be10m-12m, for materials, which is relatively expensive and inconvenient to make large areas (such as pavement materials), reverberation chamber method will be greatly limited in use. Normal-incidence absorption coefficient can only reflect material’s sound-absorption properties to plane wave perpendicularly penetrating into materials. When hand-made sample can’t be fit with the tube wall, random error is larger, and the absorption coefficients of the same kind of sound-absorbing material obtained by the two methods is numerically different.This article fully describes the basics of acoustic and sound-absorbing material, studies sound-absorption principle of sound-absorbing material, analysis the acoustic field character-istics of reverberation chamber and impedance tube, introduceds the experimental principles of reverberation chamber method and impedance tube method, and tests existing several sound-absorbing materials by reverberation chamber method and impedance tube method. Noise and vibration control analysis software Artemis is used to calculate the reverberation time T60of the sound-absorbing materials, then random-incidence absorption coefficient as is calculated. Analysis software PULSE is used to calculate the normal-incidence absorption coefficient ao. Last, based on the theory of regression analysis, regression models between two kinds of absorption coefficient are established. The best regression model is selected by hypothesis testing different models. Finally it is concluded that there’s a corresponding relationship between the random-incidence absorption coefficient αs and the normal-incidence absorption coefficient α0.