Experimental verification of additively manufactured stacked multi-wedge acoustic black holes in beams for low frequency

Abstract

Noise from machine vibrations and oscillations is a growing problem in today’s society. The use of acoustic black holes (ABH) in the area of passive vibration damping as an absorbing metamaterial is an active research field. Previous work has been successful mainly in the higher frequency range above 1500 Hz. This work aims at vibration damping in the lower frequency range below 1500 Hz. Here, additively manufactured multi-wedge ABH with two, three, four and ten wedges were welded to a beam structure and measured to estimate which number of wedges produces the best damping for a specific frequency range. The manufactured wedges largely absorbed a vast amount of the vibration energy induced into the structure and showed promising results. It was found that the more wedges were welded to the beam, the more natural frequencies occurred in the low frequency range. In the case of the ABH with ten wedges, ten eigenmodes were detected in this range, all of which absorbed the induced vibration energy effectively in the low frequency range.