Two years ago, scientists at the University of Bristol discovered that certain types of moths evade bats via sound-absorbing scales on their body. New research now suggests that wallpaper inspired by those scales could be used to block out unwanted noises.
Bats locate moths in the dark by emitting ultrasonic calls that reflect off the insects' bodies. Some moths are able to hear those calls, and take evasive action accordingly. The 2020 study focused on other types of moths that are deaf, and therefore unable to hear the bats' calls.
It was found that those moths had instead evolved special scales on their wings and thorax, which absorb up to 85 percent of incoming sound energy. As a result, the echolocation calls are poorly reflected, making it difficult for bats to find the moths.
At the time, the scientists wondered how effective the scales' sound-absorbing characteristics might be at blocking noises other than bat calls. The new U Bristol study explored that question further.
A team of researchers started by cutting 8-mm discs out of the wings of euthanized deaf Chinese oak silk moths (Antheraea pernyi), then placing those sections on same-sized aluminum discs. When a speaker pointed at the discs emitted ultrasound signals, the wing tissue was found to absorb as much as 87 percent of the sound energy – and it did so over a wide range of frequencies and angles.
What's more, the material accomplished this feat even though it was very thin. In fact, the layer of scales was just one fiftieth the thickness of the wavelength of the sound it was absorbing.
It should be noted that the ultrasound signals used in the study were above the range that can be heard by humans. The scientists are confident that a manmade version of the wing scales could be adapted to work against noises that we can hear, however, and they now hope to develop such a material.
"Moths are going to inspire the next generation of sound-absorbing materials," said the lead scientist, Prof. Marc Holeried. "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."
The research is described in a paper that was recently published in the journal Proceedings of the Royal Society A.
Source: University of Bristol
