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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。
Aiming at the problem that low-frequency sound absorption is difficult to achieve for the thin-film sound-absorbing structure with low back cavity depth, a solution to the negative magnetic stiffness is proposed. The transfer matrix method is used to establish the theoretical model of the negative stiffness thin film sound absorption structure. The acoustic impedance of the structure is equivalent to that of the conventional thin film sound absorption structure with large back cavity. The impedance tube experiment shows that under certain magnetic field conditions The resonant frequencies of negative stiffness films with different back cavities were significantly lower than those of negative ones without negative stiffness, and the curves of sound absorption coefficients were in good agreement with the theoretical ones. The negative stiffness mechanism can reduce the resonant frequency of the film’s acoustic absorption structure and realize the low-frequency sound absorption with a smaller back cavity so as to realize the design of the thin-type low-frequency acoustic absorption structure.