Moth wings as metamaterial sound absorbers

Abstract

Providing healthy living and working environments in our ever-noisier world necessitates increasing use of noise control technology. The rapidly expanding field of acoustic metamaterials has led to the emergence of ultrathin subwavelength sound absorbing methods, allowing sound insulation to be thinner and lighter than ever before. We will present our discovery of a natural acoustic metamaterial and show our ongoing work towards bioinspired metamaterial absorbers. Our bioinspiration arises from the 65-million-year acoustic arms race between echolocating bats and their moth prey, which has turned the wing scales of moths into an omnidirectional, ultrathin (1/100 λ) and broadband absorber of ultrasound (peak α = 0.71) that provides acoustic camouflage against bats. Our lithographically produced up-sized scale replicas absorb sound and can resonate at the most important frequencies for human communication. This research paves the way for bioinspired broadband sound absorbers that are thinner and lighter than existing solutions.