Sound-absorbing 'weapon' helps moths fight bats

A team of experts at the University of Bristol found that the scales on the moth's wings act as effective sound absorbers even when placed on artificial surfaces, Phys reported on June 14. The new study is published in the journal Proceedings of the Royal Society A: Mathematical and Physical Sciences.

Close-up of a scale of a moth's wing.

Bats and moths engaged in an acoustic "arms race" between hunter and prey about 65 million years ago, when bats evolved echolocation. Moths are subject to enormous predatory pressure from bats and have developed a variety of defenses to survive. The scales on their wings are key to noise cancellation.

"What we needed to know first was how effective moth wing scales would be if placed in front of a highly reflective surface, like a wall. We also needed to find out if the absorption mechanism changed. how the scales interact with this surface," said Marc Holderied, a professor at the University of Bristol's School of Biological Sciences.

Professor Holderied and his colleagues placed tiny pieces of moth wings on an aluminum plate, then examined how the orientation of the wings to the incoming sound and how removing the scales affects absorption. .

As a result, they found that the moth's wing is a very good sound absorber, even when placed on a solid substrate, it can still absorb up to 87% of the incoming sound energy. This capability is also very broad and omnidirectional, covering a wide range of frequencies and incident angles of sound.

"Even more impressive is that the moth's wings do so despite being extremely thin, with scales only 1/50th the thickness of the wavelength of sound they absorb. This extraordinary performance shows that moth wings are 'supernatural'. surfaces' (materials with unique properties and abilities that cannot be achieved with traditional materials) absorb sound in nature," explains Dr. Thomas Neil, lead author of the study. .

The ability to create ultra-thin sound-absorbing panels makes a lot of sense. As cities become louder, the need for effective and non-invasive noise reduction solutions increases. Thin and light sound-absorbing panels can also have a big impact on the travel industry by reducing the weight of planes, cars, and trains, increasing the efficiency of these modes of transport, and reducing fuel use. and reduce CO2 emissions.

The team of scientists intend to design and build material prototypes based on the sound absorption mechanism of moths. Absorption in moth wing scales is in the ultrasonic frequency range. The next challenge was to design a structure that would work at lower frequencies while keeping the ultra-thin structure like a moth's wing.

"Moths inspire new sound-absorbing materials. New research indicates that one day, you could adorn your home with ultra-thin, sound-absorbing wallpaper, using the design mimics the way moths 'camouflage' from echolocation," concludes Holderied.