J2230203 静電型MEMSスピーカーの検討

Abstract

Recently the realization of the electrostatic speaker is expected with the popularization of smartphones. In this paper, the structure of the electrostatic MEMS speaker is suggested and the characteristic is measured. The electrostatic MEMS speaker has a comb-drive actuator which vibrate in a longitudinal direction. The speaker can be drive with zero bias by introducing the Potassium-ion electret into the comb-erectrodes. The design concept of this device is making of the MEMS speaker which realize a sound pressure level 70〜80 dB in a rsonance frequency at 2 V with the size of the vibration board which is equal to an earphone. The sound from the fabricated speaker was heard at applied voltage 30 V and charged voltage 250 V. when the relation between the vibration velocity and the frequency was measured by the laser Doppler vibrometer, the value roughly match up to the simulation. However, the problem is that various resonance mode come about and the drive voltage is higher than the design value. In the future, the resonance mode will be confirmed and low voltage driving will realized by reviewing the design.