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Research of Hybrid Sound Absorption Based on Characteristic Impedance
ZHU Cong-yun;LI Ming-li;JIANG Chun-ying
2011, 31 (4):
185-189.
DOI: 10.3969/j.issn.1006-1355-2011.04.044
Aiming at the character that the effect of the active sound absorption is very good for low frequency acoustic wave, and poor for middle and high frequency sound wave, a new hybrid absorption system is proposed in this paper. This system consists of a layer of absorbent material and a movable rigid wall. The speed of the movable rigid wall can be adjusted in order to make the acoustic impedance of the absorption material match the acoustic impedance of the air, so that the absorption coefficient of the hybrid system can reach the maximal. A numerical calculation and an experiment are carried out for the case of normal incident plane wave. Both results show that the absorption coefficient of the hybrid system can reach 0.8-1.0 in the frequency range of 100-2 000 Hz, but the absorption effect of the system has not been improved very much when the frequency of the sound wave is higher than 2 000 Hz.
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