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In order to escape from bats’ hunt through sound, some of the moths have therefore evolved a “stealth coat” — made of tiny hairs and a layer of scales(磷片) — that reduces their detectability through echolocation(回声定位).

Mare Holderied, a biologist at the University of Bristol, wanted to know how good the moths were at hiding from bats. So he shaved off their hairs and then sent sound waves towards them, imitating how bats might echolocate to find their prey.

It turned out the moths’ one and-a-half-millimeter layer of fur reduced their detectability by just over 40％. In addition to the fur, moths also have a thin layer of scales, tens to hundreds of thousands of them, on each wing. The scales each respond to specific frequencies of sound waves and when a bat’s echolocation signals hit the moth’s wings, the scales start to shake. The acoustic energy (声能) from the echolocation is thus absorbed.

Dr. Holderied and his colleagues tested how well the scales worked and found that they were as good at absorbing sound as the fur. They absorbed as much as 87% of the incoming sound energy, but at only one tenth of the fur’s thickness. In terms of their ability to absorb sounds, the moth’s scales outperform and are much thinner than any human-designed soundproofing(隔音) used in homes and offices.

Recognizing the significant impact of noise on human health, especially in urban environments, Dr. Holderied’s team has been taking inspiration from the sound-absorbing proper tics of moths to design wallpaper that can reduce the noise of road traffic. Dr. Holderied concluded, “One day it will be possible to adorn the walls of your house with super-thin sound absorbing wallpaper, using a design that copies the mechanisms from moths. Moths are going to inspire the next generation of sound absorbing materials.”