扬声器低频谐波失真的数值分析

扬声器作为一种非线性振动系统，在低频段仅考虑力学恢复力非线性可用经典的Duffing方程来描述；同时考虑恢复力和磁场非线性可用广义的Duffing方程来表征。Yoshinisa研究了仅含恢复力非线性扬声器低频非线性现象中的低频谐波失真现象，但对恢复力和磁场非线性同时存在的扬声器低频谐波失真问题未作研究。西方利用Matlab软件求解扬声器非线性振动系统的广义Duffing方程的数值解，又利用Spectra Plus频谱分析软件得到扬声器低频谐波失真与频率的关系曲线，通过分析低频谐波失真与频率的关系曲线，并着重讨论磁场的非线性对扬声器低频谐波失真的影响，得出一些有价值的结论。

Numerical analysis of total harmonic distortion of a loudspeaker in low frequency range

Using the classical Duffing equation, a loudspeaker can be modeled as a nonlinear oscillation system when only considering nonlinearity of mechanic resilience in low frequency band. Taking into account nonlinearity of mechanic resilience and the magnetic field, the generalized Duffing equation can be used. Yoshinisa has studied the total harmonic distortion (THD) in loudspeaker nonlinearity in the low frequency band caused by nonlinear mechanic resilience, while ignoring the nonlinearity of mechanic resilience and magnetic field. This paper focuses on finding the THD of nonlinear motion of the loudspeaker driven by a stable voltage source using a numerical method. The solution is obtained through numerical computation with MATLAB. The equation relating THD with frequency and the corresponding curves of THD versus frequency are obtained through spectral analysis using SPECTRA PLUS. This work also analyzes the influence of nonlinearity of magnetic field on THD of the loudspeaker, and draws several useful conclusions.