Electromagnetic MEMS Microspeaker for Portable Electronic Devices
Résumé
This work presents the conception, the microfabrication, and the electroacousticcharacterization of a new electromagnetic microspeaker based on silicon. Theobjectives are to get improved sound quality compared to that of conventionalmicrospeakers, while keeping the electroacoustic efficiency as high as possible. Anoptimized stiffening silicon microstructure let the sound radiator be extremely light andrigid. The mobile part is suspended to the fixed part by silicon suspension springs,which enable large out-of-plane displacement. The acoustic radiator is actuated by anelectromagnetic motor, composed of a fixed permanent magnet and a planar coillocated on top of the silicon radiator. The piston-like motion of the radiator favored bythis structure is very beneficial for the sound quality. Electro-mechano-acousticcharacterization of the microfabricated microspeaker showed that the radiator surfacecould run out-of-plane with displacements higher than ±400 μm, with no mechanicaland electrical failure. For an electrical power of 0.5 W, the microspeaker was capableto generate a sound pressure level of 80 dB at 10 cm, from 330 Hz up to 20 kHzfrequency. The efficiency reaches 3×10-5, that is to say three times more than typicalefficiency of conventional microspeakers. Moreover, as characterization resultsshowed, the existence of very few structural modes and the low electroacousticdistortions evidence the high sound quality of the microspeaker.
Domaines
Sciences de l'ingénieur [physics]
Origine : Fichiers produits par l'(les) auteur(s)
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