Vibration control using grids of acoustic Black Holes: How many is enough?

This work investigates the application of Acoustic Black Holes to the vibration reduction of plate structures. Lighter high loss damping treatments, to reduce narrow and broadband structural vibrations, are critical enablers needed for new design solutions for many noise and vibration control applications. Vehicle systems present many challenging needs due to their weight optimized structures and operational environments. In this work Finite Element and Boundary Element Models were used to evaluate the vibration performance of periodic grids of embedded Acoustic Black Holes. The end goal was to develop design guidelines for significantly reducing vibration and radiated noise levels of a target structure, while simultaneously reducing the overall structure weight. The Acoustic Black Hole cell dynamics were examined to gain insight for optimizing their performance. Global structure modes, local cell modes, and extended- (or super-) cell modes were identified and related to the observed treatment performance. Additional insight on the Acoustic Black Hole cell's "area of influence" was shown by examining the energy flow in and around the cells. The results give designers critical insight for determining the types and quantities of Acoustic Black Holes needed for specific levels of vibration reduction of critical structures.