Scales on the Wings Help Moths Defend Against Echolocation, Inspiring Experts to Develop Lightweight Noise-Reducing Materials.
A team of experts at the University of Bristol has discovered that the scales on moth wings act as effective sound-absorbing devices, even when placed on artificial surfaces, Phys reported on June 14. The new research has been published in the journal Proceedings of the Royal Society A: Mathematical and Physical Sciences.
Close-up of a moth wing scale. (Photo: University of Bristol)
Bats and moths have been engaged in a “arms race” over sound for about 65 million years, as bats evolved echolocation capabilities. Moths faced immense predation pressure from bats and developed numerous defense mechanisms for survival. The scales on their wings are key to noise reduction.
“What we first needed to know is how effective moth wing scales are when placed in front of a highly sound-reflective surface, such as a wall. We also needed to understand how the absorption mechanism changes when the scales interact with this surface,” said Marc Holderied, a professor at the School of Biological Sciences at the University of Bristol.
Professor Holderied and his colleagues placed small pieces of moth wings on an aluminum plate and then tested how the orientation of the wings affected incoming sound and how the removal of scale layers influenced absorption.
As a result, they found that moth wings are excellent sound absorbers, capable of absorbing up to 87% of incoming sound energy even when placed on a solid substrate. This ability is also broad and multidirectional, covering a range of frequencies and angles of sound incidence.
“Even more impressively, moth wings achieve this despite being extremely thin; the scales are only 1/50th the thickness of the sound wavelength they absorb. This extraordinary performance indicates that moth wings are a ‘super surface’ (materials with unique properties and capabilities that cannot be replicated with traditional materials) for sound absorption in nature,” explained Dr. Thomas Neil, the lead author of the study.
The ability to create ultra-thin sound-absorbing panels has significant implications. As cities become noisier, the demand for effective and non-intrusive noise reduction solutions is increasing. Lightweight sound-absorbing panels could also greatly impact the travel industry by reducing weight for airplanes, cars, and trains, enhancing efficiency while reducing fuel consumption and CO2 emissions.
The team of scientists plans to design and fabricate prototypes of materials based on the sound absorption mechanism of moths. The absorption in moth wing scales lies within the ultrasonic frequency range. The next challenge is to design a structure that operates at lower frequencies while maintaining the ultra-thin structure like that of moth wings.
“Moths inspire new sound-absorbing materials. This research suggests that one day, you may decorate your home with ultra-thin sound-absorbing wallpaper, using designs that mimic how moths ‘camouflage’ themselves against echolocation,” concluded Holderied.
