While cochlear implants have been around for a while, they aren't true "bionic ears." There are still external components, such as a microphone.

Now a team of engineers at the University of Utah and Case Western Reserve have built a device that could put more of the components inside the ear, making them more convenient, as well as less bulky.

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In a normal ear, sound comes in through the ear canal, hits the eardrum and causes it to vibrate, which sends a chain of vibrations through tiny bones called the malleus, incus and stapes. The stapes hits the cochlea, a fluid-filled chamber, and that moves the hair cells on its inner membrane. That in turn stimulates the auditory nerve, which carries the sound signals to the brain.


Darrin J. Young, an associate professor of electrical and computer engineering at the University of Utah, moved the external components inside the ear and came up with another way to stimulate the auditory nerve. Sound moves through the ear canal to the eardrum, which vibrates as it does normally. At the point where the eardrum connects to the malleus, called the umbo, a tiny acceleromoter is implanted to pick up the vibrations. The accelerometer is attached to a chip, and together they serve as a microphone that picks up the sound vibrations and converts them into electrical signals that reach the cochlea via electrodes.

That's very different from an ordinary cochlear implant, which has the microphone, signal processor and transmitter placed outside the ear.

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To date, tests have all been done on cadavers, so while the researchers know that the device works (the sound signals are being transmitted to the right parts of the ear and vibrating the umbo), that doesn't tell anyone what the experience might be like for patients. Tests in living patients are still a few years away.

There is also still work to be done in improving the microphone, which has some trouble with lower-frequency, quieter sounds. The charger for the device would also still be external, just as in conventional cochlear implants.

Photo: A tiny microphone is shown attached at right to a cadaver’s umbo, where the eardrum (under left part of device) meets the hearing bones. The device measures about one-tenth inch by one-quarter inch.

Credit: Case Western Reserve University / University of Utah