Vibration damping of plates using waveguide absorbers based on spiral acoustic black holes

Abstract

We propose a waveguide absorber (WGA) based on an acoustic black hole (ABH) to damp vibrations in plate structures. The proposed WGA is composed of a spiral ABH and a rod connecting it to the surface of the plate. The geometrical dimensions of the WGA are determined, such that it has a lower cut-on frequency than a given target range of frequencies, by using a recently developed impedance method for curved ABHs. We then optimize the location of attachment and direction of the WGA on a simply supported uniform plate to minimize the peak levels of its surface-averaged mobility. The strategy used to find its optimum location and direction is based on an analysis of structural intensity that provides the distribution and direction of elastic wave energy propagating in the plate. The results of simulations and experiments show that large reductions of resonance peaks could be achieved below 500 Hz by attaching a couple of lightweight WGAs to a uniform plate. With practical applications in mind, we also applied the ABH-based WGAs to plates that form a box structure, where this is a simplified and scaled version of a box-type mechanical system.