Direct experimental verification of the sound-induced tunable resonance on a flexible electrorheological layer

Abstract

The tunable behaviors of low-frequency sound waves transmitted through a flexible electrorheological (ER) layer with plastic-aluminum electrodes are investigated. It shows that, within 80–210 Hz, the sound-pressure level (SPL) decreases with the electric field E, while within 210–300 Hz, the SPL increases with E. The vibration displacement of the ER layer surface is directly measured via a laser Doppler vibrometer. It reveals that two resonance modes exist on the ER layer and all the modes are tunable via the electric field. Around the first resonant frequency of 100 Hz, the vibration displacement decreases with the increase of E, while around the second resonant frequency of about 180 Hz, the vibration displacement increases with E. The consistently varying characteristics with respect to the electric field imply an intrinsic relation between the vibration of the ER layer and the sound transmission. The relation is further qualitatively explained by the vibration-radiation model. The tunable resonance effect in the ER layer would be useful in constructing tunable phononic crystals and other acoustic devices.