Cricket-inspired hearing aids

04 September 2018

Interview with 

Rob Malkin, University of Bristol

AFRICAN-FIELD-CRICKET

African Field cricket Gryllus bimaculatus

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We're all very familiar with crickets, but how can something so small as a cricket make such a racket? And how is this potentially able to inform the technology of tomorrow? Chris Smith spoke to Rob Malkan from the Faculty of Engineering at the University of Bristol…

Rob - Well they've been around for 400 million years. They've been evolving and in that time they've come up with incredibly elegant simple and efficient ways of turning sound into some kind of information. We've been at microphones and speaker design for 150 years, so there's a huge amount of information there that can help us to inspire the next generation of microphone or speaker, or even auditory signal processing and things like that.

Chris - Seems funny to think that 21st and 22nd Century technology could be informed by something hundreds of millions of years in the making!

Rob - Absolutely, and - you know - my background is physics and materials science, and when I first became interested in this field and started working with colleagues in the biology department I was amazed. You know, I'd see really elegant solutions to real engineering problems that maybe the biologists themselves weren't necessarily aware of. You know it's a goldmine of information really.

Chris- What particular challenge are you hoping to solve?

Rob - A personal driver for me is, you know, I have some friends and colleagues who happen to use hearing aids; and if you ever speak to them about what their auditory life is like when they use hearing aids, it's not so great in certain ways, actually. One of the big things is when they're in a room - you know - in a pub or in a restaurant or something, they really struggle to pick out the conversation of the people around them. And the reason is that the microphones are picking up sound from all around and all that information is really complicated and difficult to understand if you have a hearing aid. So one thing you'd like to be able to do is to take some inspiration from some insects, for example you know there's a fly called the ormia, it’s a nocturnal fly and it's able to detect the source of a sound within two degrees. Humans we can generally do it for around 10 degrees so these little ears that the ormias have can detect sound really accurately so it would be amazing if you could have some microphones in the hearing aid that you could switch to like a conversation mode so it will ignore all the sound from everywhere else other than forwards so the person you're talking to you'll be able to hear them really clearly and everything else is essentially muted.

Chris - So how does the insect achieve that? Because that really is very impressive, and sound engineers struggle to achieve that sort of performance on a day to day basis. So something that's as simple as an insect is doing this with no electricity whatsoever...

Rob - Well this is the really amazing thing. Only recently have we come up with the technology to be able to actually understand what it is that the insects themselves are doing. How is the ear moving. What's the it made of? You know, it's just one thing knowing what ingredients are that go into making an insect ear. But when we use electron microscopes and things like this, we're finding that the ear isn't really a material, the ear is a structure. These ears are so thin that it's 600 nanometres thick much much you know the thickness of a human hair that kind of size but within that thickness is different materials laid down in different orientations. So really it's not a material it's a structure and those ears, they've integrated the three processes which we used to hear. So we tend to hear in three stages we hear the sound collected by air to air, we amplify it in the middle ear and then we process it in our cochlea and then that signal gets into the brain. The insects do that all three of those things on the ear itself they collect it they amplify it and they process it on the ear all mechanically, no electricity, nothing. So that's really the key is to try and understand the physics of it a little bit. And we're trying to see that in exactly how we're going to improve the next generation of hearing aids and any any microphone really to speak of themselves.

Chris - So could you take what the insects do and then effectively 3D print a miniature artificial version that basically works the same way except will interface with the electronics in hearing aid. So that user can focus the direction of pick up on what they're looking at so they get rid of all these distracting sounds.

Rob - Excellent question and essentially the answer is not yet. You've got two types of making something one is you remove material like you start with a block of metal and remove it mechanically or you start at the bottom with very low scale nano printing 3D printing techniques and insects and all these structures are just about in the middle there and really we're not quite there in terms of engineering we know how these insects work and how their ears work but I think the technology to replicate them could be you know maybe a good 10 - 20 years off.

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