Small plate vibration sound-absorbing device with a clearance and without surrounding restriction: Theoretical analysis and experiment

This article focuses on the theoretical analysis and experiment of a small plate vibration sound-absorbing device with a clearance and without surrounding restriction. Generally, a plate vibration sound-absorbing device absorbs sound in a frequency range lower than that of porous material, which is used as a sound-absorbing material, and its sound absorption coefficient is small. Furthermore, note that the plate is fixed at the periphery in a conventional plate vibration sound-absorbing device. Hence, when the plate is small, vibration barely occurs and effective sound-absorbing effect is not obtained. Given that the plate vibration sound-absorbing device has a restriction wherein a particular size of plate is required, it is primarily utilized for indoor finishing considering the architectural acoustics, and finding applications for small-sized machines has been challenging. Theoretical values in this work are calculated assuming that the clearance and back air layer for the small plate vibration sound-absorbing device constitute a Helmholtz resonator. Furthermore, experiments were conducted to perform comparisons against the theoretical value. The theoretical analysis was conducted by connecting the clearance and back air layer in parallel with the plate portion in the electrical equivalent circuit. By performing the experiments using various parameters, the sound absorption characteristics of the proposed plate vibration sound-absorbing device were determined. If the clearance is smaller than the boundary layer thickness, then the conventional resistive end correction cannot be applied.