Influence of Phase-Shifted Vibration of Diaphragm Sections on the Response and Distortion of Dynamic Headphones
The acoustical measurement of frequency response and distortion of dynamic headphones usually show irregularities in the fundamental and second harmonic in the range above 2 kHz. To evaluate design rules for diaphragms under consideration of nonlinearities, the mechanical oscillation process has been examined. Using the Laser-Doppler-Interferometry, the values and relative amplitudes of higher eigenfrequencies have been estimated by measuring the velocity of the diaphragm in the matrix of points. Due to the values of frequency showing higher distortion, only eigenvectors with radial-symmetric contribution have been determined. In order to check the possibility of a mathematical description and simulation the first 10 radial-symmetric eigenfrequencies and eigenvectors have been calculated using the finite-element method on a personal computer. The correspondence of measurements results and simulation result is discussed.
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