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Research on a Numerical Simulation Method about Harmonic Distortion of Loudspeaker

X. Lu[1]
[1]Zhejiang Electro-Acoustic R&D Center, CAS, Zhejiang, China

扬声器的失真问题一直受电声业界的关注,尤其是谐波失真,它是影响扬声器重放声音音质的主要因素之一。 本文提出了一种基于 COMSOL Multiphysics® 软件预测扬声器谐波失真的仿真分析方法。该方法需建立包括磁场、振动系统和声场等多个物理场的扬声器的全模型,给扬声器加载一单频电压信号,用瞬态分析的方法可求解得到该频率激励下的扬声器的多个重要物理量随时间的变化函数,如流经音圈的电流I(t)、音圈的受力F(t)、振动系统表面上任意点的位移x(t),以及声场中任意点的声压P(t)等。给扬声器加载一个时间长度为0.1s的单频电压信号,仿真分析所得的防尘帽顶点的位移曲线 x(t) 如图1所示,图2则是对应的在扬声器正前方0.1m处的声压曲线 P(t)。 再对所得的声压信号的稳态部分做FFT频谱分析,便可获得输入信号的各阶次谐波分量,进而计算得到该扬声器的各次谐波失真及总谐波失真。表1给出了一款扬声器在两个激励频率点的总谐波失真的仿真分析结果,其中的测量结果是对所分析模型对应的扬声器单体的THD测量结果。 结论:基于 COMSOL Multiphysics® 软件,采用扬声器磁路、振动系统和声场的三场耦合的瞬态分析方法,可比较准确地预测扬声器的谐波失真。

Abstract: In order to predict the harmonic distortion of loudspeakers, a numerical simulation method is proposed. This method models magnetic circuit, vibration system and sound field of loudspeaker by COMSOL Multiphysics® Software. Transient analysis is applied to calculate the property parameters of time-domain such as coil current I(t)、Lorentz force F(t)、displacement x(t) and sound pressure P(t), then post processing such as FFT of the P(t) is needed to calculate harmonic distortion. Structural damping is applied to the structural model in order to obtain a realistic response. This method is verified at some frequencies primarily.
Keywords: loudspeaker; numerical simulation; harmonic distortion; transient analysis