Rob Malkin is on a mission to develop the next generation of hearing aids. And he’s looking to insects for inspiration. Alan Barker attended the 2016 Isambard Kingdom Brunel Award Lecture at the British Science Festival and marvelled.

The human ear, you might think, is a triumph of evolution. It picks up sound through the ear drum, amplifies it with the three tiniest bones in the body, and processes frequencies in the cochlea. It’s remarkably sensitive: as we listen to a person whispering, our ear drum vibrates by about the width of a hydrogen atom.

But their very sensitivity makes our ears vulnerable. We lose high frequencies as we age and can easily damage our ears through exposure to sound at a (not very high) volume. The Royal National Institute for Deaf People estimates that, by 2035, upwards of 15.6 million people in the UK will suffer from hearing loss.

Current technological solutions are good – but not that good. The most sophisticated hearing aids perform relatively poorly compared to a human ear. And cochlear implants, though giving remarkable results for many people, are almost useless for processing music. When it comes to acoustic design, we could do better.

And yet the technology used in hearing aids has hardly changed for decades. Take microphones: they operate much the same as they did a century ago. Good quality audio typically requires large devices, which require significant signal processing. They also tend to function poorly in noisy environments. We need to miniaturise, but we also need to reconceptualise our notions of microphones and loudspeakers.

Engineer Rob Malkin from the University of Bristol, had the notion of investigating insects for inspiration. After all, mammals have evolved just one acoustic design; insects, at different times, have evolved no fewer than 16. In the Isambard Kingdom Brunel Award lecture at this year’s British Science Festival, Rob showed how insects could help us build bio-inspired acoustic devices.

Take the locust. It has huge ears on the sides of its chest, about 2mm in diameter, which vary in thickness, allowing the insect to pick up and amplify sound with the same device. Rob and his team made a replica with a 3D printer, which worked well.

Locust

Fruit flies are so small that they are unable to have a traditional ear on their body, and have adapted their hairs to act as the sound receivers. The hairs are about 0.1mm long, and so sensitive that, if scaled up to the size of the Eiffel Tower, they would vibrate by just one millimetre. The New Zealand Weta, perhaps the creepiest insect of all time, has a simple, levered ear on each leg.

Weta

Katydids have recently been shown to have a cochlear-based hearing organ barely visible to the human eye, yet with capabilities which are comparable to our own.

Katydid

Rob is seeking to engineer a bio-inspired microphone: tiny and tough, it would require no signal processing or amplification and could isolate individual sound sources (making conversations in loud environments clear and pleasant). The potential in mobile phones and other devices is obvious; but, more than anything, Rob wants to bring clear and natural hearing to the hard-of-hearing.

Nonetheless, he warned us that, however good the solutions he and his colleagues devise, they will almost certainly never surpass the unique, exquisite delicacy of the human hearing system. So, he urges, we should look after it.

Alan Barker, Swansea British Science Festival, September 2016. Alan Barker is a writer and training consultant specialising in communication skills.  He is Managing Director of Kairos Training Limited.

Image banner: Cochlea of the inner ear, Dr David Furness Wellcome Images, 2011