Research On The Prediction Of Nonlinear Distortion For A Micro-speaker

With the development of science and technology,portable electronic products such as laptop and cellphone have developed rapidly,and micro-speaker is an important device in these electronic products.In this paper,the influence of nonlinear parameters on the frequency response and total harmonic distortion of micro-speaker is analyzed.Based on the influence of nonlinear mechanical stiffness and nonlinear force coupling factor,the influence of nonlinear mechanical resistance is considered,and a method for predicting nonlinear mechanical resistance is proposed.The effects of three main nonlinear parameters,mechanical stiffness,force factor and mechanical resistance,on total harmonic distortion are analyzed and verified by experiments.The research contents are summarized as follows:On the basis of the nonlinearity of stiffness and force factor in the differential equation of vibration system,a new nonlinear differential equation is formed by adding the nonlinear mechanical resistance,and the nonlinear differential equation is solved by Runge-Kutta numerical method.Based on the solution of the equation,the frequency response curve and total harmonic distortion curve of the micro-speaker are calculated and verified by experiments.A method for predicting the nonlinear mechanical resistance is proposed.The nonlinear acoustic resistance caused by the magnetic gap and the small hole on the bottom cover of the micro-speaker is considered in this method.The nonlinear acoustic resistance is converted into the equivalent nonlinear mechanical resistance on the diaphragm by using electric acoustic analogy method.The accuracy of the prediction method is verified by comparing the measured results.COMSOL Multiphysics is used to simulate the stiffness of the suspension and the force factor respectively to obtain the stiffness curve and the force factor curve,which are in good agreement with the measured results of the parameters,thus ensuring the feasibility and accuracy of the simulation acquisition of the two main nonlinear parameters.The comparable nonlinear parameter curve is constructed,and the total harmonic distortion under three kinds of nonlinear parameters is calculated by using the theoretical calculation model established in this paper to explore the influence of nonlinear parameters on the nonlinear distortion of micro-speaker.