Resonant Frequency Analysis of the Diaphragm in an Automotive Electric Horn

The resonant frequency of the diaphragm is the important parameter in the design of electric horns. The natural frequency of vibration of the diaphragm is dependent of the stiffness and also the mass attached to it as the diaphragm is designed as a thin plate. A magnetic field is used to produce the excitation of the diaphragm mass and resonance occurs when the two frequencies coincide. It is also important to maintain the air gap between the diaphragm mass and the magnetic core. Presently, the development time used in introducing new horns is high and is mostly based on trial and error. It was therefore decided to try out an analysis using ANSYS to cut down development time. This paper enumerates a design process of horn diaphragm that was carried out using ANSYS. The finite element model of the diaphragm with the mass is subjected to modal and harmonic analyses to determine the natural and the resonant frequency conditions. The stress-strain characteristic of the particular diaphragm design is also analyzed. Variations have also been brought in the diaphragm design and also the mass attached to the diaphragm. The results have corroborated the experimental frequency data obtained using a Fast Fourier Transform (FFT) analyzer. The procedure will be helpful to quickly fine tune electric horns, thereby reducing development time appreciably.

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