Harnessing Multiple Internal Reflections to Design Highly Absorptive Acoustic Metasurfaces

Finding sound-absorbing materials and structures is a key task in noise control. Engineered structures that can absorb sound are usually based on local resonance, but this study uses the collective response of individual building blocks to design a metasurface that soaks up acoustic energy. It is revealed that multiple internal reflections inside the blocks can increase their interaction with acoustic waves, and a little loss can lead to broadband absorption with better uniformity. This nonresonant approach to designing structures for noise control might also inspire the pursuit of other systems with enhanced wave-matter interactions.