Vibration and noise reduction for double-layer thin-wall box

Utilizing theoretical calculation and measurement of damping ratio, the mechanism in reducing vibration of viscous liquid is investigated. Aiming at the equivalent thin-wall box, the modal experiments, of which include single-layer box with various oil volume, double-layer box with various diaphragm plate distance and with various hole-number, are designed. The corresponding damping ratios are gained. Through the combined characteristic calculation based on the mean damping ratio, the whole change trends of various working conditions are studied. The results indicate that the increase of box liquid volume and the introduction of diaphragm plates can enhance the damping ratio of the system and reduce the power of acoustic radiation of the system. Especially, compared with diaphragm plates without holes, diaphragm plates with holes do not further increase the damping ratio of system, but have better damping characteristics in the high frequency band.