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研究了驱动频率低于扬声器辐射体薄壳轴对称模态最低固有频率的扬声器1/2分谐波失真。采用以位敏探测器作为光电传感器的激光三角法实验观测扬声器振膜的振动位移和模态,确定了参与的非轴对称模态的周向波数。采用多尺度法求解了扬声器的非线性模态方程。给出了扬声器分谐波的阈值电压公式。结果表明扬声器辐射体薄壳的分谐波失真源于直接激励的轴对称模态耦合激发了非轴对称模态的振动,这种耦合激励表现为参数激励。增大扬声器振膜材料的损耗因子、杨氏模量和厚度可提高产生分谐波的阈值电压。
The 1/2 subharmonic distortion of the loudspeaker, whose driving frequency is lower than the lowest natural frequency of the shell axisymmetric mode of the speaker radiator, is studied. The vibrational displacement and mode of the loudspeaker diaphragm were measured by the laser triangulation method using the position-sensitive detector as a photoelectric sensor, and the circumferential wavenumber of the non-axisymmetric modes involved was determined. The multiscale method is used to solve the nonlinear modal equation of loudspeaker. The threshold voltage formula of the subharmonic of the speaker is given. The results show that the subharmonic distortion of the shell of the speaker radiator originates from the axisymmetric modal coupling of the direct excitation which excites the vibration of the non-axisymmetric mode. The coupling excitation manifests as the parameter excitation. Increasing the loss factor of the diaphragm material of the loudspeaker, the Young’s modulus and the thickness increase the threshold voltage at which subharmonic waves are generated.