Experts from the University of Bristol have found that moth wing scales act as excellent sound absorbers, even when placed on an artificial surface.
Researchers, who recently discovered that moth wings provide acoustic protection against the echolocation cries of bats, investigated whether their structure could inform sound-absorbing panels that performed better, when not moving in free space.
Bats and moths have been involved in an acoustic arms race between predator and prey since bats developed echolocation about 65 million years ago. Moths are under tremendous predation pressure from bats and have evolved a plethora of defenses in their fight for survival, but it is the scales on a moth’s wing that hold the key to survival. the transformation of noise canceling technology.
Professor Marc Holderied, from Bristol’s School of Biological Sciences, said: ‘What we needed to know first was how well these moth scales would perform if they were in front of an acoustically highly reflective surface, like a wall.
“We also needed to find out how absorption mechanisms might change when scales interacted with this surface.”
Professor Holderied and his team tested it by placing small sections of moth wings on an aluminum disc, then systematically tested how the orientation of the wing relative to incoming sound and the elimination of Tartar layers affected absorption.
Remarkably, they found that moth wings proved to be excellent sound absorbers, even when they were above a solid acoustic substrate, with the wings absorbing up to 87% of sound. incoming sound energy. The effect is also broadband and omnidirectional, covering a wide range of frequencies and angles of sound incidence.
“What’s even more impressive is that the wings do this while being incredibly thin, with the layer of scales being only 1/50th the thickness of the wavelength of sound they make. absorb,” explained lead author Dr. Thomas Neil. “This extraordinary performance qualifies the moth wing as a natural sound-absorbing metasurface, a material that has unique properties and capabilities not possible with conventional materials.”
The ability to create ultra-thin sound absorbing panels has huge implications in building acoustics. As cities become noisier, the need for effective non-intrusive noise mitigation solutions increases. Likewise, these lightweight sound absorbing panels could have huge impacts on the travel industry, with any weight savings in planes, cars and trains increasing the efficiency of these modes of transport, reducing fuel consumption and CO2 emissions.
Scientists now plan to replicate the sound absorption performance by designing and building prototypes based on the sound absorption mechanisms of the moth. The absorption they characterized in moth wing scales is in the ultrasonic frequency range, above that which humans can hear. Their next challenge is to design a structure that will operate at lower frequencies while maintaining the same ultra-thin architecture used by the moth.
Professor Holderied concluded: “Moths will inspire the next generation of sound deadening materials.
“New research has shown that one day it will be possible to decorate the walls of your home with ultra-thin sound-absorbing wallpaper, using a design that copies the mechanisms that give moths stealthy acoustic camouflage.”
‘Moth wings as sound absorber metasurface’ by Thomas R. Neil, Zhiyuan Shen, Daniel Robert, Bruce W. Drinkwater and Marc W. Holderied in Proceedings of the Royal Society A.