Nicky Blackburn
April 1, 2007, Updated September 13, 2012

The idea that you can hear sounds from vibrations transmitted through your teeth is nothing new. Long before composer Beethoven held a wooden baton between his teeth and pressed it to his piano to listen to the notes, inventors have been experimenting with a variety of hearing aids devised from wooden boards held to the teeth. Imaginative though these were, up to now, there has never been a practical solution.

Audiodent, a small Israeli start-up based in Omer, near Beersheva, is about to change all that. The company has developed an innovative new hearing aid that clips easily inside the mouth, using the teeth and jawbone to transmit sound to the brain.

In the US alone, 28 million people suffer from some degree of hearing impairment. Of these, however, only six million use hearing aids. That means that 80% of people with a hearing problem do not use any kind of hearing aid, and of those that do, an estimated 40% of them are dissatisfied.

“This shows clearly that people have issues with hearing aids,” says Eyal Aharon, the CEO of Audiodent. For a start, he explains, sound quality is poor. “A hearing aid is a very small device that must carry out complex computations. Because of its size, the device is limited in terms of computing resources and memory.”

In challenging noise environments, for instance, like the loud hotel cafe where Aharon now sits, most people using a hearing aid would simply turn it off and rely on lipreading, because the surrounding noise drowns out voices. Aside from affecting sound quality, the tiny size also makes hearing aids difficult to handle and even adjustments to volume are hard to manage, particularly for the elderly.

Present hearing devices are uncomfortable, particularly those placed inside the ear, which plug up the ear and prevent the user from experiencing natural spatial awareness. Some patients opt for an even more radical approach, having a hearing aid implanted surgically into their head.

Finally, says Aharon, hearing aids have a stigma attached to them. “So many people say that whenever they put their hearing aid on people treat them as if they had 30 points less on their IQ,” he says.

Audiodent’s hearing aid, which will cost about the same as traditional hearing aids (about $1,500 with accessories) is made up of two parts. The first is the mouth unit, which fits snugly into the mouth with the aid of two hooks used traditionally by dentists to fit temporary crowns. This can be attached to a real or artificial tooth, preferably on the upper jaw.

The second part, still in development, is an external unit, which connects wirelessly to the hearing aid, and which can fit into another item, like jewellery, a smart card, a cell phone, or a device the size of an MP3 player.

According to Aharon, Audiodent’s hearing aid offers better sound quality – with the external unit allowing for the introduction of new software that can improve sound dramatically.

“When cell phones first came in it was impossible to use them in noisy situations such as a hotel bar, or outside in the wind, but today cell phones include a great deal of software designed to improve this experience,” Aharon tells ISRAEL21c. “Today you can use your cell phone just about anywhere and you will be able to hear without problem. This software cannot be included in current hearing aids because they are too small, but it can be included in ours. There are endless possibilities.”

Because the control device is external and larger in size than current hearing aids, users can also manage it more easily, selecting different programs as necessary.

Secondly, the internal device, which can be used by children and adults, is comfortable and leaves the ears open. It is the same size as a bridge, and the mouth easily adapts.

“It might feel strange the first day but you get used to it quickly and soon forget about it,” asserts Aharon.

Finally the mouth unit is invisible, hidden away behind the teeth, and the external unit can be camouflaged as something else. “You can wear it round your neck, put it in your pocket or on the table. No-one will think that by having one of these items you have a hearing aid,” says Aharon.

He decides to illustrate what he’s talking about. “I always find the best way to understand what we are doing is to try it yourself,” he explains. He unwraps the device and asks me to hold the mouth unit between my teeth. He then turns up the volume on an MP3 connected to the external unit and the strains of Louie Armstrong’s “It’s a Wonderful World” clearly fill my head. Not from my ears, as I’m used to, but uncannily from somewhere inside my head.

This is bone-transmitted sound, with the teeth acting as a path to the skull bone. The vibrations of sound do not bypass the outer ear or middle ear, as they would normally do, but travel straight to the cochlear canal in the inner ear. Once they arrive there the vibrations shake the auditory nerve floating in lymph, enabling me to hear the sound.

“So why didn’t anyone do this before if the idea has been around so long?” asks Aharon suddenly. The reason, he answers himself, is that the previous inventions were simply too large to be workable. Audiodent, however, has developed, and patented, a miniature battery with low energy consumption that can be used inside the device for 24 hours.

“This was vital if we were going to make this work,” says Aharon. “You couldn’t have a battery that ran out after an hour. We developed a battery that allows significant power saving compared to any other device on the market today. The user can put it in, in the morning, and take it out at night. Recharge it for an hour, and then use it again the following day.”

Audiodent was founded by three dentists, two Israeli and one French. They started playing with the idea of a hearing aid in the mouth because their patients complained that the noise of the drill was so loud inside their heads. They tried earplugs, but nothing could drown out the sound. The dentists thought about this, and decided to try to use this phenomenon to their advantage.

The dentists started developing the idea in the mid ’90s and patented a number of their ideas, but nothing was formalized until 2003, when Aharon joined the team. Self-funded through the first years, the company finally raised NIS3.1 million from Israeli Venture capital fund Ma’ayan Ventures in August 2006.

The company has now developed a prototype of its device and tested it on a number of patients suffering various forms of hearing impairments in preliminary clinical trials. The results of these, says Aharon, have been better than expected.

“When we began testing this device, experts told us that if we could help people with a hearing impairment of 30DB then we would be in great shape, but our demonstration proved that we can reach people with hearing impairments of up to 60-70DB, in all frequencies, low as well as high. Some people still don’t believe it’s true,” says Aharon.

The company also carried out tests on word discrimination and found that the Audiodent hearing aid increased word discrimination from 80%, without an aid, to 94%. “The teeth transfer the sound very well,” says Aharon.

Today the company employs three people full time, and works with about 15 subcontractors. Three of the world’s top ear, nose and throat experts, from Israel, the US, and the UK, have also come on board, offering their expertise to the company.

Audiodent is now looking to raise an additional $3 million from international investors, which will take the company to a completed product and sales.

While the hearing aid is undoubtedly Audiodent’s first target market (over 6.2 million hearing aids were sold in 2004 at a value of about $2.5 billion), there are many other potential applications for this technology. For a start, the company plans to include the external unit within cell phones, to create mobile phones for the hearing impaired. There are other possibilities, however.

“We have a device that can send out sounds to you wirelessly, even if you are not in the same location, and no-one will know. It doesn’t have to be short range, it can be any range we want. Think about a newsreader, or security personnel. People can listen without any visible sign of doing so,” says Aharon. “This opens so many opportunities, options and possibilities that we are playing with and dreaming about. It’s very exciting.”

The staff of Audiodent are not the only dreamers. “My daughter wants the device to be ready before final exams,” Aharon admits with a laugh. “She wants me to read the correct answers to her from back home.”

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