Just as people with sight in only one eye have problems with depth perception, those with impaired hearing in one ear, known as unilateral hearing loss (UHL) or single-sided deafness (SSD), face difficulty in localizing sound. Addressing the problem with a hearing aid worn in the mouth might not sound like a logical solution, but that’s just what medical device company Sonitus Medical is doing with SoundBite - a hearing system that transmits sound to the inner ear via the teeth.
The SoundBite system consists of a small unit worn behind the ear (BTE) and an in-the-mouth (ITM) hearing device that is custom made to fit either the upper left or right back teeth. The BTM unit captures the sound and wirelessly transmits the signals to the ITM device, which sends imperceptible vibrations via the teeth near-simultaneously to both cochleae.
Behind-The-Ear Unit The BTE unit features a microphone that sits in the canal of the impaired ear to take advantage of the acoustic benefits provided by the patient’s own ear. This microphone is connected to the BTE unit by a small translucent tube. The BTE unit uses a digital signal processor to process the sound and a second microphone for noise cancellation. After the sound has been processed it uses a wireless chip to transmit the signals to the ITM device.
In-The-Mouth Unit The ITM device contains a sealed flat, rechargeable battery, wireless receiver, and a small actuator that converts the wireless signals received from the BTE into vibratory energy, which travels via the teeth, through the bones to the cochleae. The device is custom made to fit the wearer’s upper left or right teeth and all the components are hermetically sealed inside a dental grade acrylic that has been used for making dentures for years.
Unlike conventional hearing aids that employ air conduction to turn up the volume of sound traveling into the ear, the SoundBite relies on bone conduction and as such, does not require a functional middle or outer ear to deliver sound. There are already Bluetooth headsets such as the Motorola Endeavor HX1 that use bone conduction as a means to transmit sound to the ear so its possible that systems similar to the SoundBite could be used for future Bluetooth headsets.
The SoundBite system is currently undergoing clinical trials for the treatment of SSD, but planned future applications for the technology from Sonitus Medical include conductive and mixed hearing loss as well.