Moth wings inspire sound absorbing wallpaper

Installers delivering acoustic treatments could soon have a new tool in their toolbox in the form of moth-inspired, sound-absorbing wallpaper.

Researchers at the University of Bristol in the UK discovered that scales of moth wings act as excellent sound absorbers and have been studying whether their structure could help create better performing sound absorbing panels.

Moths developed the noise-cancelling scales as protection from bats that locate and prey on the insects using sound waves.

In a press release Professor Marc Holderied, of 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, such as a wall.

“We also needed to find out how the mechanisms of absorption might change when the scales were interacting with this surface.”

Professor Holderied and his team tested this by placing small sections of moth wings on an aluminium disc, then systematically tested how orientation of the wing with respect to the incoming sound and the removal of scale layers affected absorption.

Their research showed that moth wings were excellent sound absorbers, even when on top of an acoustical solid substrate, with the wings absorbing as much as 87% of the incoming sound energy. The effect is also broadband and omnidirectional, covering a wide range of frequencies and sound incident angles.

“What is even more impressive is that the wings are doing this whilst being incredibly thin, with the scale layer being only 1/50th of the thickness of the wavelength of the sound that they are absorbing,” explained lead author Dr Thomas Neil. “This extraordinary performance qualifies the moth wing as a natural occurring acoustic absorbing metasurface, a material that has unique properties and capabilities, that are not possible to create using conventional materials.”

Now the scientists plan to replicate the sound absorbing performance by designing and building prototypes based on the sound absorbing mechanisms of the moth. The absorption that they have characterised in moth wing scales is all in the ultrasound frequency range, out of the range of human hearing. They now plan to design a structure that will work at lower frequencies whilst retaining the same ultrathin architecture employed by moths. 

Professor Holderied concluded: “Moths are going to inspire the next generation of sound absorbing materials.

“New research has shown that one day it will be possible to adorn the walls of your house with ultrathin sound absorbing wallpaper, using a design that copies the mechanisms that gives moths stealth acoustic camouflage.”

Top image credit: Wirestock Creators/Shutterstock.com

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