In the reverberation room, the absorption coefficient is measured by the composite structure of perforated plate, perforated plate and porous sound absorbing material, and the sound absorption characteristics of perforated plate are studied. Through the analysis of the data ,it is founded that: under different thickness of the cavity D, the peak value of sound absorption coefficient of perforated plate is maintained is about 0.35; the resonance frequencies of the perforated plate decreases

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... nuously along with the increase of the thickness of the cavity D, distributed in 250 ~ 630Hz.Perforated plate with composite structures of different absorption material is under the different thickness of the cavity D, and the peak value of the absorption coefficient is maintained at 0.7~0.85;the resonance frequency of the composite structure decreases with the increase of the cavity thickness D , distributed in 200 ~ 500 Hz. The width of the absorption band has no obvious relation with the thickness of the cavity D, but it has a great relationship with the perforated plate which is added to the sound absorption material.