By Karina Shah
Earless moths have sound-absorbent wings that act as acoustic camouflage from preying bats. The moth wings have an ultrathin layer of scales that absorb sound and could be adapted for noise-cancelling technology.
Marc Holderied at the University of Bristol, UK, and his colleagues projected sound waves at the wings of two species of earless moths (Antheraea pernyi and Dactyloceras Lucina). They found that the sound waves that bounced back from the moth wings were much quieter.
By using an imaging technique called acoustic topography, the team found that these moth wings have a layer of scales that are arranged in a special repeating pattern that absorbs sound across a wide range of frequencies.
“Similar to how stealth bombers are less detectable by enemy radars, the moths have developed a stealth coating against the bat’s sonar,” says Holderied. The moth wings, which are around a tenth of a millimetre thick, absorb the specific sound waves produced by bats.
Bats interpret their surroundings using echolocation: they send out sound waves and when the sound hits an object, an echo is produced. The bats use these echoes to build an image of their environment. Because the earless moths’ wings absorb these sound waves, they remain largely undetected, improving their chances of survival.
Other moths have ultrasensitive ears to hear bats, but the deaf, earless moths rely on this sound-absorbent layer to evade their predators.
Holderied and his team also compared the earless moths with two species of butterflies and found that only the moths had the sound-absorbing quality.
Although these wings only absorb sound heard by bats, it could be adapted for human sound frequencies, says Akito Kawahara at the Florida Museum of Natural History. This could prove useful in applications such as sound absorber panels and noise-cancelling earphones.https://6d7eb335d5c4a142237e5ab7aef5c561.safeframe.googlesyndication.com/safeframe/1-0-37/html/container.html
Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.2014531117
More on these topics: