Biomimetic Microperforated Sound Absorbers

The scales on moth wings show an unequalled ability to absorb sound, which they have acquired as a defence in a 65 million-year-long acoustic arms-race with their main predator - echolocating bats. We discovered that moth wings are 10x more efficient than traditional sound absorbers used in architectural acoustics. This renders the underlying mechanism a highly promising source for bio-inspired noise control solutions that can help provide quieter and hence healthier living and working conditions for all of us. Manmade noise is the second highest environmental health risk and on average costs each European 1.3 days of healthy live every year. Better sound absorbers are required in our fight against noise pollution, and the mechanism discovered on moth wings offers a true step change in such technologies.

One part of the remarkable ability of moth wings to absorb sound is that they act as an acoustic metamaterial (the first know in nature) based on a multitude of differently tuned resonant sound absorbers (individual scales on the wing; BBSRC and EPSRC funded). We have implemented this mechanism for the human hearing range, filed a respective patent in summer 2023, and built sound absorber prototypes using this principle. Our existing prototypes do not fully reach the acoustic performance of moth wings though, and our preliminary modelling suggests another, hitherto unexploited feature of these moth wings might be the missing factor - the highly intricate 3-dimensional double-layered nano-porosity of their wing scales. Our modelling suggests that this double nano-porosity, which is not currently captured in our designs, can provide an extremely powerful 50% performance boost. Remarkably, this double nano-porosity is only found in silk moths whose wings have the best sound absorber performance. Objectives: In this project we will (a) identify and fully characterise the respective nanostructures, (b) extract the key features and functional mechanism, (c) translate these into the frequency range humans can hear, (d) build and test respective prototypes and finally, (e) implement this additional feature into our current resonant sound absorbers to boost their performance. Such a gain (50%; 6dB) is substantial, e.g. because every reduction in noise level by 3dB allows employers to double staff exposure time in noisy work environments. Aims and target markets: The key outcome of this project will be translation of our fundamental bioacoustics research into innovative bio-inspired sound absorbers that outperform existing solution up to 10 times. This provides a unique selling point in a wide range of sizeable markets where space, weight or cost of noise control is a key objective. Sound absorbers have a global market value of $20 billion per annum for absorber materials alone. We are currently completing Innovate UK ICURe Explore (Advanced Materials call) training for market exploration and have identified the following target markets (i) sound deadening for studios, offices, and homes (sound-absorbing wallpaper); (ii) automotive passenger comfort; and (iii) aerospace cabin noise control. We have had extremely positive early responses with several NDAs in place or currently being developed. This funding will help us exploit an essential untapped potential to better meet our identified market expectations. Our customised range of revolutionary noise control solutions will provide global technological leadership to the UK acoustics sector (£4.6b pa; 16.000 employees).