Most people picture a hearing aid as a small device that sits at or in the ear and sends sound along the ear canal. Bone conduction hearing aids use a different route. They send sound as vibration through the bones of the skull. This article is a plain-English explainer of how that works and how the main types are put together. It is general information about the technology and does not say whether any type is relevant to any individual.
Two Routes Sound Can Take
Sound normally reaches the inner ear by passing through the outer ear and the middle ear. Our plain-English tour of ear anatomy shows where each part sits. This is often called air conduction, because the sound travels as air pressure waves down the ear canal before being passed along inside the ear.
Bone conduction is the alternative route. The National Deaf Children's Society (NDCS), a UK charity, explains that bone conduction devices send sound vibrations through the bones in the skull to the inner ear, bypassing the outer and middle ear. The inner ear itself does the same job either way. NDCS describes the cochlea as converting the vibrations into electrical signals, which the brain interprets as sound.
What Is Inside the Device
A bone conduction hearing aid has the same basic idea as other hearing technology: a microphone picks up sound, and a processor works on it. The difference is the output. NDCS describes the microphone turning sound into vibrations, rather than into amplified sound played into the ear canal. The part that creates the vibration is usually called a vibrator or transducer.
NDCS adds that the vibrator sits on the mastoid bone, the large bone behind the ear.
The Non-Surgical Version
The simplest arrangement holds the device against the head from the outside. NDCS says aids with a separate vibrator are typically worn on a metal or soft fabric headband, called a softband, or sometimes on the arms of glasses. Sound processors that combine all the parts into one unit are usually worn on a soft fabric headband or a sticky pad.
Hearing Australia also describes non-surgical bone conduction aids as being used on a headband or hat.
The Implanted Versions
Other designs involve a small implant placed in the bone during a procedure. Hearing Australia notes that there are both surgical and non-surgical options with bone conduction devices. NDCS describes two broad styles of implant:
- Percutaneous (abutment): NDCS says the fixture protrudes through the skin and directly stimulates the bone. The sound processor attaches to the part that sits outside the skin.
- Transcutaneous (magnetic): NDCS says the skin remains intact, and the vibrations are transmitted through the skin to the implant.
Implanted types involve surgery, which is a decision for a medical specialist. This article describes how the hardware is arranged, not what any operation involves or what result anyone can expect.
Where These Devices Sit Among Hearing Technology
Whether any device category is relevant to a particular person is a question for a hearing assessment and, for implants, a medical specialist.
It is also useful to know that bone conduction is a different category from a cochlear implant. A cochlear implant works by a separate method, and our article on hearing aids vs cochlear implants compares them in general terms. The wider range of devices is outlined on the hearing aid solutions hub.
A Few Terms You Will Meet
Articles about this subject often use the term conductive hearing loss. NDCS defines conductive deafness as when sound cannot pass effectively through the outer and middle ear. That definition explains why the bypass idea is described the way it is. For the wider picture of how conductive and sensorineural hearing loss differ, see our article on the difference between conductive and sensorineural hearing loss.
The details of any device, including how it is worn and what it is designed to do, are set out in its manufacturer documentation.
A Quick Summary
- Bone conduction hearing aids send sound as vibration through the bones of the skull to the inner ear, bypassing the outer and middle ear.
- The device has a microphone, a processor and a vibrator, which sits on the mastoid bone behind the ear.
- Non-surgical versions are held on by a headband, adhesive pad or glasses arm. Implanted versions involve surgery.
- Whether a device category is relevant is a matter for a hearing assessment and, for implants, a medical specialist.
If you'd like to chat about your hearing, the friendly team at CQ Audiology in Rockhampton is here to help. You can read about hearing aids in Rockhampton, call (07) 4848 6528 or book online.
This article is general information, not personal medical advice. For advice about your own hearing, speak with your GP or a hearing care provider.
Sources: National Deaf Children's Society, UK charity (Bone conduction hearing devices; Devices worn on a headband); Hearing Australia (Bone conduction hearing aids; Implantable devices).
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