Alberich型吸声覆盖层的低频吸声机理分析

Mechanism analysis of Alberich sound-absorption coating at low-frequency

声波垂直入射Alberich型吸声覆盖层时激起沿厚度方向传播的轴对称波,而决定覆盖层低频性能的最低阶波可等效为"准平面波",通过共振特性分析了覆盖层的低频吸声机理,指出达到低频有效吸声需要满足的轴对称波相速度的近似条件。低频吸声机理要点包括:①吸声覆盖层的共振是粘弹性圆柱腔体的共振;②吸声覆盖层的吸声峰值频率对应覆盖层的反共振频率而不是共振频率;③绝对软背衬的最低吸声峰频率比绝对硬背衬低一半左右。

The axisymmetric wave propagating along thickness direction of Alberich sound absorption coating is excited in case of normal incidence, and the axisymmetric wave with the lowest order, which determines the low-frequency performance of sound absorption, can be approximated as a quasi - plane wave. The mechanism of sound absorption of Alberich coating was analyzed by using the resonance theory, and the relationship between the phase velocity of axisymmetric wave and the lowest peak frequency of absorption coefficient was obtained. It was shown that the mechanisms of the sound absorption at low-frequency include that： （1） the coating resonance is referred to as the resonance of a viscoelastic cylindrical tube; （2） the peak frequency of absorption coefficient is corresponding to the anti-resonant frequency of the coating, rather than its resonant frequency; （3） the lowest peak frequency of absorption coefficient in the case of soft backing is half of that in the case of rigid backing.