How a Tiny Fly Has Helped Hearing Aids

Research is constantly being done to help advance hearing aid technology and provide better hearing opportunities for those individuals who struggle with hearing loss. Looking to the way that sound waves are processed, called signal processing, researchers try to find ways to amplify sound in a way that can be heard by those hearing impaired individuals. This is combined with research that uses technology to design and manufacture hearing aids that have the best fit, construction, and durability. Some of the most interesting research lies in the tiny fly Ormia ochracea that are being studied by the National Institute on Deafness and other Communication Disorders (NIDCD) and other researchers. Using the hearing capabilities of animals has helped researchers further understand how human hearing can be benefitted and assisted, and this tiny fly has provided a lot of useful information.

The Ormia ochracea is a small (1 cm in length) yellow nocturnal fly whose tiny ears are only a half millimeter apart. What is extraordinary about this little fly is that most flies have no hearing capabilities whatsoever, but the Ormia ochracea can determine the direction of a sound within two degrees; this is something that has only been previously seen in humans, owls, and cats. The miniscule distance between this fly’s ears is notable because it is the distance that helps with localization cues. The very small difference in time in which sound arrives at each ear, and the sound pressure level work together to provide binaural cues that are used to help us determine sound direction, as found in the research of Norman Lee and Andrew Mason.

The Ormia ochracea needs this refined hearing ability to find a certain species of cricket that it parasitizes. The male cricket, Teleogryllus oceanicus, produces a song to attract the female mates using a system of opening and closing the wings, and using a plectrum, or scraper, to rub against a vein on the wing. The Ormia ochracea is amazingly able to locate this sound, and use the mating call to it’s own advantage. The female fly lays her eggs on and around the male cricket host, and the larvae burrow in the cricket, eat and grow, and eventually kill the cricket host roughly  7 days later.

The Ormia ochracea needs incredibly accurate hearing to be able to locate this particular cricket, and a neurobiologist at Cornell, Ron Hoy, has tested just how incredible this hearing is in a unique experiment, as told in Scientific American:

They tethered the tiny fly to a Ping-Pong ball, which functioned as a spherical treadmill. The ball was dotted so that a computer could track the movement of the ball, and thus the fly. The researchers then played artificial cricket sounds from various locations and observed the fly’s movements. They found that Ormia could detect directional changes as small as two degrees. “Even humans trying to detect who is speaking in a crowded room can’t do better than that”, team member Andrew Mason of the University of Toronto remarks.

It was further discovered that the fly’s ear drums beat out of phase with each other, and it is that pressure difference that helps the fly to locate the source of the sound. Humans are making this calculation in about 10 microseconds, but the fly can compute it in about 50 nanoseconds. The speed at which Ormia ochracea can calculate the location, and the accuracy, is what has prompted researchers to study this fly and try to apply the mechanisms used to hearing aids. Ormia ochracea utilizes a unique hearing mechanism with the eardrums located behind the head. The eardrums are acting as microphones, and they amplify the sound and indicate the direction in which the sound came from. The Biomimicry Institute points out how this unique structure is different from a traditional microphone:

Unlike a regular microphone, whose hearing "membrane" is clamped down on all sides, Ormia's hearing mechanism consists of two membranes fastened with a hinge in the center so that it rocks like a see-saw. If sound waves come on both sides at exactly the same time and with the same amplitude, the see-saw doesn't move. But if sound comes to one side before the other, it moves because the two pressures are unequal.

The implications of this research have been felt throughout the hearing aid industry, and has led to further exploring just how small hearing aids can be (think of the smallest hearing aids available placed next to a fly). The smaller the hearing aids, the less intrusive and cumbersome they are for the wearer. The other boon of this research is the directional nature of the fly’s hearing, and how that could translate to human hearing. One of the biggest complaints of hearing aid users is that hearing in a noisy environment is difficult; the different sounds become jumbled together and it is hard to pick out that one voice you want to hear. The solution to this is directional hearing aids, which could be greatly helped by the see-saw mechanism found in the fly’s hearing. The see-sawing of the microphones receiving the sound could both reduce power consumption, saving battery life, and help maintain calibration. Somehow this little fly is not only able to determine where the noise of their host cricket is coming from, but they are able to do it in the midst of all of the noises of their natural environment. This is promising for hearing aid technology, and for getting rid of the “cocktail party” phenomenon that plagues impaired listeners in noisy situations.

Hopefully, the tiny but powerful Ormia ochracea will prove to be an asset to the hearing aid technology industry. As researchers work to fully understand the intricacies of this fly’s hearing capabilities, Neal Hall (assistant professor of electrical and computer engineering at the University of Texas) captures the wonder found in Ormia ochracea’s ability :

It is the equivalent of if you were just standing on the ground and all of a sudden the ground starts shaking because there was an earthquake, and I told you I can tell just by my feet that the epicenter of the earthquake was in Costa Rica. The fly does something equally remarkable in locating sound given the proximity of its ears.

Hearing aids have come a long way, and the possibility of harnessing a tiny insect’s hearing power to further innovate is exciting. Factory Direct Hearing is proud to offer the latest in new hearing aids, and are constantly on the forefront of hearing aid technology. We want to partner with you to provide hearing solutions—contact us to get started.