扬声器非线性特性的Hilbert-Huang变换分析

Analysis of nonlinear behaviour of loudspeakers using Hilbert-Huang transform

为研究扬声器的非线性特性和形成机理,提出一种基于Hilbert Huang变换(HHT)的扬声器非线性特性分析方法.该方法通过对扬声器纸盆位移信号进行经验模态分解(EMD)得到内禀模态函数(IMF),计算出 IMF函数的瞬时频率.用瞬时频率的变化表示纸盆位移信号波内频率调制的非线性现象,直接反映出与扬声器结构相关联的非线性特性.仿真和实际扬声器实验结果表明,用HHT瞬时频率表示扬声器非线性的方法与传统的傅立叶谐波方法相比,能更确切地说明产生非线性的原因,给扬声器非线性的改善与补偿提供了依据.

A new method based on Hilbert-Huang transform (HHT) was proposed to describe and characterize the nonlinearities of loudspeakers. In this method, the displacement signal of the diaphragm of loudspeakers was decomposed into a set of intrinsic mode functions (IMF) by a process called empirical mode decomposition (EMD). The instantaneous frequencies of IMFs were obtained by using classical Hilbert transform. The variations of the instantaneous frequencies indicated the nonlinearity caused by the intrawave frequency modulation of the diaphragm's displacement signal, and characterized the loudspeaker nonlinearities relative to the parameters of loudspeakers. The results of simulations and experiments on a practical loudspeaker show that the instantaneous frequency can characterize more intuitively and actually the nonlinear features of loudspeakers than the conventional Fourier harmonics, and is helpful for compensating for the nonlinearities and for improving the quality of sound reproduction.