磁力负刚度薄膜结构低频吸声特性

针对背腔深度较小的薄膜吸声结构难以实现低频吸声的问题,提出了磁力负刚度的解决方法。采用传递矩阵法,建立了负刚度薄膜吸声结构理论模型,分析得出该结构的声阻抗等同与大背腔常规薄膜吸声结构的声阻抗;阻抗管实验验证得出,在一定磁场条件下,不同背腔的负刚度薄膜吸声结构与无负刚度结构相比其共振频率显著下降,吸声系数曲线与理论结构吻合。负刚度机制能够降低薄膜吸声结构的共振频率,用较小背腔实现低频吸声,从而实现薄型低频吸声结构设计。 

Low frequency sound absorption of a membrane-type absorber with magnetic negative stiffness

A membrane-type absorber usually requires a large back cavity for the low frequency sound absorption.In order to design a compact low frequency membrane-type absorber,magnetic negative stiffness was introduced to reduce the stiffness of the back cavity.With the use of the transfer matrix method,a theoretical model was established by introducing the negative stiffness mechanism to the model.It is demonstrated that a small cavity with the negative stiffness can simulate the acoustic impedance of a large cavity without and shift the absorption peak frequencies downwards.During the experiments,the absorption peaks at different cavities are downwards obviously in a given magnetic field due to the negative stiffness.Analytical results are compared with the experimental data from the impedance tube test.Good agreement validates that the negative stiffness can shift the absorption peak frequencies downwards and implements a compact design for the low frequency membrane-type absorber.