采用特性阻抗匹配的半主动组合吸声材料与结构

摘要

由于主动吸声在低频声波入射时方有吸声效果,而在中高频声波入射时,吸声效果不明显.鉴此,采用一种新的半主动吸声方法；即由一层吸声材料和可移动的刚性壁组合结构,改变刚性壁移动的速度,使吸声材料的表面声阻抗与空气的阻抗相匹配,从而使吸声材料的吸声系数达到最大.最后,对平面入射声波进行了数值计算与实验,结果表明:在100～2 000 Hz时,吸声系数能达到0.8～1.0,而对于更高频率的入射声波,用此方法进行纯主动吸声的效果改善不明显.%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.