Brief Summary

Research at Bristol University has highlighted the very real prospect of replacing acoustic absorbers which are presently multiple inches thick with very specialised wallpaper which uses the structure of Moth wings to achieve the previously impossible. We have the details.

Going Deeper

When it comes to creating optimal acoustic environments in recording studios, mixing rooms, and post-production facilities, finding the right balance between space efficiency and effective sound absorption is crucial. Recent groundbreaking research by experts at the University of Bristol has shed light on an unlikely source of inspiration: The scales on moth wings. Their findings suggest that the unique structure of these wings could revolutionise the way we approach acoustic treatment, paving the way for ultrathin sound absorbing wallpaper. This presets exciting possibilities for audio professionals.

Acoustic Arms Race

For millions of years, bats and moths have engaged in an evolutionary arms race shaped by the predator-prey relationship. Bats developed echolocation around 65 million years ago, forcing moths to evolve various defence mechanisms to survive. Among these adaptations, it is the scales on moth wings that hold the key to this transformative sound absorbtion technology.

Led by Prof Marc Holderied from Bristol's School of Biological Sciences, the research team aimed to assess the performance of moth wing scales when placed on acoustically reflective surfaces, such as walls. Their experiments involved systematically testing the wing orientation and the removal of scale layers to understand how these factors affected sound absorption.

Remarkably, the team discovered that moth wings functioned as excellent sound absorbers, even when positioned on top of solid acoustic substrates. The wings absorbed up to 87% of the incoming sound energy, showing a broadband and omnidirectional effect across a wide range of frequencies and angles. Adding to this, the moth wings achieved this performance despite their incredibly thin structure. In fact, the scale layer is only 1/50th the thickness of the wavelength of the absorbed sound.

The scientists now aim to replicate the moth wing's sound absorbing performance by designing and building prototypes based on its mechanisms. The current absorption characteristics pertain to the ultrasound frequency range, beyond the range of human hearing. The next challenge for the research team involves developing a structure that operates effectively at lower frequencies while maintaining the moth's ultrathin architecture.

This isn’t the first time we’ve reported on innovative approaches to passive acoustic treatment. Back in 2017 we reported on an innovative approach to low frequency absorbtion which involved reducing the required thickness of material by slowing the speed of sound. You can read more about this in this article in Nature. I mention this parallel development because it’s possible this might be a complementary technology which could extend the range of absorption below what this new ultrathin absorbtion might be able to achieve.

The prospect of ultrathin sound absorbtion, utilizing a design that mimics the moth's stealth acoustic camouflage, is very appealing to professionals. Though this technology not only promises efficient acoustic treatment for recording studios and post-production facilities but also presents a broader impact on various industries where noise reduction and lightweight materials are paramount.

As audio professionals, we can eagerly anticipate the advancements in ultrathin sound absorbing metamaterials inspired by moth wings. In the near future, these innovations may enable us to optimise acoustic environments without compromising valuable space. With more and more people working from home and fewer mixes happening in purpose-built spaces the compromise between treatment and space has never been more keenly felt. The evolution of acoustic treatment is well underway, and the future looks remarkably promising.

More On Acoustics

For more information on acoustics and studio design. Check out our podcast extra with Andy Monro from 2017.