A close up image of a butterfly wing showing a scale on the surface.  These absorb the echolocation calls used by bats to find prey and effectively hide it from their predator.

Scientists use moth wings to absorb sound and could be used to make noise-canceling wallpaper

Go ahead and order this drum kit, because noise wallpaper might not be too far off.

Scientists have found that when they mount tiny sections of moth wings on a hard surface, they are able to absorb up to 87% of incoming sound waves.

The University of Bristol research team first discovered that the unique scales on the wings of moths absorb the echolocation calls used by bats.

The sounds they absorb are all at too high a frequency for humans to hear, so further work is needed to narrow the range of absorption to practical use.

But in the future, we may be able to mimic this noise wing texture on the exterior of buildings to absorb traffic noise, or to reduce aircraft weight.

Professor Marc Holderied from the School of Biological Sciences said: “Moths will inspire the next generation of sound-absorbing 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.”

A close up image of a butterfly wing showing a scale on the surface. These absorb the echolocation calls used by bats to find prey and effectively hide it from their predator.

A close-up image of a scale found on a moth's wing, showing its unique ribbed structure

A close-up image of a scale found on a moth’s wing, showing its unique ribbed structure

Moths are under tremendous predation pressure from bats and have evolved a plethora of defenses in their fight for survival, including their unique structure that absorbs echolocation calls.

Moths are under tremendous predation pressure from bats and have evolved a plethora of defenses in their fight for survival, including their unique structure that absorbs echolocation calls.

ECHOLOCATION AND MITES

Bats hunt at night using echolocation, where they use sound waves and echoes to determine the location of their prey

Moths are under enormous predation pressure from bats and have evolved a plethora of defenses in their fight for survival

Scientists from the University of Bristol discovered in 2020 that the scales on the wing of butterflies act as sound absorbers, making them almost invisible to their nocturnal predator.

Male hawkmoths have also been known to rub their genitals against their abdomens to emit a high-pitched ultrasonic squeal that scares off some bats.

An elephant sphinx

An elephant sphinx

Bats acquired the ability to “see” in the dark using echolocation around 65 million years ago.

Echolocation is where an animal emits sound that reflects off nearby objects, allowing it to image its surroundings in low light and find food.

Moths are under enormous predation pressure from bats and have evolved a plethora of defenses in their fight for survival.

British scientists discovered in 2020 that the scales on the wing of butterflies act as sound absorbers, making them almost invisible to their nocturnal predator.

They then investigated whether the wing structure could be used on sound absorbing panels when not moving in free space.

Professor Holderied 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 absorption mechanisms might change when scales interacted with this surface.”

Scientists glued small sections of moth wings to an aluminum disc before systematically testing its absorbency.

Wing sections were tested with and without the scales attached, both on the upper and lower surfaces of the wings.

They examined how sound absorption was affected by the orientation of the wing relative to incoming sound and the number of layers of wing scales used.

It was revealed today, in the newspaper Proceedings of the Royal Society Athat the wings absorbed up to 87% of incoming sound energy, even when mounted on a sound-absorbing substrate.

The noise cancellation effect is also broadband and omnidirectional, covering a wide range of frequencies and angles of sound incidence.

Lead author Dr Thomas Neil said: “What’s even more impressive is that the wings do this while being incredibly thin, with the scale layer being only 1/50th the thickness of the wavelength of the sound they absorb,

“This extraordinary performance qualifies the moth wing as a natural sound-absorbing metasurface, a material that has unique properties and capabilities that are impossible to create using conventional materials.”

a: Location of wing samples taken from the butterfly species Antheraea pernyi for testing.  b: Experimental setup to characterize the angular distribution of the sound reflection of samples of wings and metal disc.  c: Wing sections were tested with (intact) and without (bald) the scales attached, both to the upper (dorsal) and lower (ventral) surfaces of the wings

a: Location of wing samples taken from the butterfly species Antheraea pernyi for testing. b: Experimental setup to characterize the angular distribution of the sound reflection of samples of wings and metal disc. c: Wing sections were tested with (intact) and without (bald) the scales attached, both to the upper (dorsal) and lower (ventral) surfaces of the wings

Graph showing the reflection coefficient of different surfaces when exposed to sounds of different frequencies.  The higher the reflection coefficient, the less the surface absorbs sound.  Left: upper surface of the wing scale (dorsal) Right: lower surface of the wing scale (ventral)

Graph showing the reflection coefficient of different surfaces when exposed to sounds of different frequencies. The higher the reflection coefficient, the less the surface absorbs sound. Left: upper surface of the wing scale (dorsal) Right: lower surface of the wing scale (ventral)

The research opens doors to using the texture of wings to create ultra-thin sound absorbing panels that could be mounted on the exterior of buildings.

Noise pollution is the second environmental cause of health problems, just after the impact of air quality.

It is linked to hearing loss, high blood pressure, heart disease, sleep disturbances and stress.

As cities become increasingly noisy with global population growth, there is a growing need for effective, non-intrusive soundproofing solutions.

Additionally, they could be used in noisy modes of transport like cars and airplane cabins to reduce their weight, and therefore fuel consumption and carbon emissions.

Further research by the Bristol scientists will involve creating prototype materials with texture based on the sound absorption mechanisms of the moth.

The absorption they characterized in moth wing scales is in the ultrasonic frequency range and above that humans can hear, the lowest being 20 kHz.

The next challenge is to design a structure that will operate at lower frequencies while maintaining the same ultra-thin architecture used by the moth.

How moths use their fur coats to make them undetectable to bats

You might think Invisibility Cloaks are the stuff of science fiction and Harry Potter – but it seems the Insect Kingdom is actually onto something

Scientists have found that moths can make themselves almost invisible to bats thanks to their hairy coat

Tests revealed that 85% of the sound signals – ultra-high-pitched squeaks – that bats use to locate their prey were absorbed by moth hairs.

This reduced the distance at which a bat could detect a moth by nearly 25%, increasing its chances of survival.

Butterfly hairs are actually ‘hair-like’ scales and structurally resemble fibers used in soundproofing technology, according to research conducted by the University of Bristol

Read more here

British scientists discovered in 2020 that the scales on the wing of moths act as sound absorbers, effectively making them invisible to their nocturnal predator.

British scientists discovered in 2020 that the scales on the wing of moths act as sound absorbers, effectively making them invisible to their nocturnal predator.

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