Bone conduction devices
What is a bone conduction device?
A bone condition device is a hearing implant that converts sounds into vibrations that are sent to the inner ear via the bones in the head. Bone conducted hearing solutions are typically used by people who have a conductive hearing loss or a mixed hearing loss and whose outer ear or middle ear are not able to conduct sound properly into the inner ear. They may also be used in the event of an irritated, damaged or malformed ear canal. E.g. people who have atresia and microtia may benefit from a bone conduction device.
Bone conduction devices are also used to treat single-sided deafness (unilateral hearing loss) by sending sound from the non-hearing side to the hearing ear on the other side of the head.
How does a bone conduction device work?
Bone conduction devices make the skull behind the ear vibrate and the vibrations send signals through the bones to the inner ear. A bone conduction device does not rely on sound amplification like in the case of conventional hearing aids. Hearing through the bones is a normal way of hearing sounds. You hear approximately half of your own voice through the bone – that is why you feel your voice sounds different when you record it – you miss the part conducted by the bone. The vibrations are so small that you cannot feel them, but you can indeed hear them.
Bone conduction devices normally consist of two parts – an external and an internal one. The external part picks up sound and processes it, then sends it to the internal part which makes the bones vibrate. There are active and passive bone conduction devices. With an active bone conduction device, the skin stays intact.
Candidates for bone conduction devices must have a working cochlea that can send sound signals to the brain. Bone conduction can be considered for patients with hearing loss in one and both ears.
Surgical vs. non-surgical devices
In some bone conduction devices, the external sound processor / audio processor is attached directly to the skull and involves a minor surgery to place a small titanium implant in the bones behind the ear. A direct contact through the skin between the vibrating external part and the bone via an abutment gives efficient transmission and gives a good sound quality. Other systems, also consisting of a sound processor / audio processor and a completely implanted internal part, will provide stimulation leaving the skin intact. These systems also provide excellent sound quality. If you do not or cannot have a surgery (for instance for young children), there are non-surgical devices where the external sound processor is held against the skin either via a soft band or on an adhesive and discrete patch.
Although non-surgical solutions do not give the same hearing as implanted ones (you typically lose 10-20 dB as the sound must travel through hair and skin), it is critical to let young children hear sounds and they should be used as early as possible. Non-surgical solutions are also a way of testing how you will hear after.
Do not restore hearing
Patients with bone conduction devices generally hear very well and report a natural sound quality. This is because the inner ear is either completely healthy (in the case of conductive hearing loss) or only slightly damaged (in the case of mixed hearing loss) and the damaged part is by-passed by bone conduction devices.
Candidate for a bone conduction solution?
If you think that a bone conduction device may be relevant for you, you should contact an ENT-doctor or an audiologist.
Other types of implants:
Middle ear implant
Auditory Brainstem Implant (ABI)