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

By Jacky On Jun 15, 2022

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

Scientists have found that when they mount small pieces of butterfly wings on a hard surface, they can absorb up to 87 percent of the incoming sound waves.

The University of Bristol research team initially found that the unique scales on moths’ wings absorb echolocation calls from bats.

The sounds they absorb are all at a frequency that is too high for humans to hear, so more work is needed to lower the absorption range to be practically used.

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

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, with a design that mimics the mechanisms that give moths stealth acoustic camouflage.”

A close up view of a moth’s wing with a scale on the surface. These absorb echolocation calls used by bats to find prey, effectively hiding them from their predator

A close-up image of a shell found on a moth’s wing, with its unique ridged structure

Moths are under tremendous predation pressure from bats and have evolved a plethora of defense mechanisms in their pursuit of survival, including their unique structure that absorbs echolocation calls

ECHOLOCATIONS AND MOTHS

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

Moths are under enormous predation pressure from bats and have developed a plethora of defenses in their pursuit of survival

Scientists at the University of Bristol found in 2020 that the scales on the moths’ wing act as sound absorbers, making them nearly invisible to their nocturnal predator

Male hawk moths have also been known to rub their genitals against their abdomens to emit a high-pitched, ultrasonic squeak that deters some bats

An elephant hawkmoth

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

Echolocation is where an animal emits a sound that is reflected from nearby objects, allowing it to create an image of its environment in low-light conditions and find food.

Moths are under tremendous predation pressure from bats and have evolved a plethora of defense mechanisms in their pursuit of survival.

The British Scientists discovered in 2020 that the scales on the moths’ wing act as sound absorbers, making them nearly invisible to their nocturnal predator.

They went on to study whether the wing structure could be used on sound-absorbing panels when you are 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 placed in front of an acoustically highly reflective surface, such as a wall.

“We also had to figure out how the absorption mechanisms might change if the scales interacted with this surface.”

The scientists glued small sections of the moths’ wings to an aluminum disc before systematically testing its absorbency.

Wing sections were tested with and without the scutes on both the upper and lower wing surfaces.

They looked at how sound absorption was influenced by the wing orientation relative to the incoming sound and by the number of wing layers used.

It was revealed today, in the news Proceedings of the Royal Society Athat the wings absorbed as much as 87 percent of the incoming sound energy, even when mounted on a sound-absorbing surface.

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

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

“This extraordinary performance qualifies the moth wing as a naturally occurring acoustically absorbent meta-surface, a material with unique properties and capabilities not possible with conventional materials.”

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

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

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

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

It is associated with hearing loss, high blood pressure, heart disease, sleep disorders and stress.

As cities become louder with population growth, there is a growing need for efficient and non-intrusive soundproofing solutions.

In addition, they can be used in noisy modes of transport such as cars and airplane cabins to reduce their weight, and thus fuel consumption and carbon emissions.

Further research from the Bristol scientists includes creating prototype materials with textures based on the moth’s sound-absorbing mechanisms.

The absorption they have characterized in moth wing shells is all in the ultrasonic frequency range and above what humans can hear, the lowest being 20 kHz.

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

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

You might think that invisibility cloaks are the stuff of science fiction and Harry Potter — but it seems the insect kingdom is really up to something

Scientists have discovered that moths can make themselves almost invisible to bats thanks to their furry fur

Tests found that 85 percent of the sound signals — ultra-high-pitched beeps — bats use to locate their prey were absorbed by the moths’ hairs

This reduced the distance a bat could detect by nearly 25 percent, increasing its chances of survival

Moth hairs are actually scales “that resemble hairs” and are similar in structure to the fibers used in soundproofing technology, according to the study led by the University of Bristol.