Flies inspire hearing aid technology

Special directional hearing aids are being developed

Flies with extra strong hearing could be used to help develop hearing aids for humans, say scientists.

The parasitic Ormia ochracea fly is less than one centimetre in length, but its hearing is so acute it can determine the direction of a sound within two degrees.

Scientists used to think that only keen-eared owls, cats and humans possessed this special directional hearing, but the research published in Nature has found the fly's hearing is particularly good.

Most flies have no sense of hearing at all but the Ormia specialises in detecting singing crickets.

They deposit their tiny larvae on them and when they grow into maggots they eat the crickets from the inside out.

These flies possess one of the most accurate and efficient auditory systems in the animal kingdom which is critical to their survival

Professor Andrew Mason

The fly's ears act as an extremely small, simple and sensitive directional microphone.

Now a new generation of hearing aid technology and nanoscale microscopes, based on the flies ears', are being developed.

Directional hearing

And scientists hope the new technology will help them make special directional hearing aids that are smaller and cheaper than hearing aids currently available.

This would enable the hearing impaired to tune into specific things and filter out background noise - making it easier for them to decipher what one person was saying in a crowd of people.

Zoology professor Andrew Mason in the Division of Life Sciences at the University of Toronto and the lead author of the study said their research showed the flies had remarkable hearing.

He said: "Their sense of hearing is remarkable because their ears are so close together that directional hearing would be impossible in any other animal.

"Our results demonstrate that in terms of directional hearing, the flies are as good as any system known.

"These flies possess one of the most accurate and efficient auditory systems in the animal kingdom which is critical to their survival."

The Ormia fly has directional hearing

To work out how the Ormia fly was able to pinpoint sound, Professor Mason and his colleagues tethered the flies on a spherical treadmill made from a ping pong ball.

They then floated the ball on an air stream to reduce friction and to ensure the flies' walking movements were translated into the rotations of the ball.

The scientists then used an portable speaker to play artificial cricket sounds from different parts of the room.

They found that the flies then walked towards the sound and discovered they could detect changes in a sound-source location of smaller than two degrees.

Filter noise

Professor Mason said: "Even humans trying to detect who is speaking in a crowded room can't do better than that."

Dr John Low, director of technology at the Royal National Institute for Deaf People (RNID), said the research would benefit the hard of hearing.

"A major problem faced by people with a hearing loss, of which there are almost nine million in the UK, is the ability to pick out individual sounds against a background of noise.

"RNID therefore welcomes any new technologies that will improve hearing aid performance in this area.

"There are many challenges in translating research into practical technologies that will benefit deaf and hard of hearing people.

"RNID is actively monitoring progress in the transfer of this research to new hearing aid development."