What is Bone Conduction?
Bone Conduction transmits sound vibrations through the skull bones directly to the cochlea, bypassing the eardrum and outer ear. It is used in sleep devices to deliver phase-locked acoustic stimulation without the risk of waking the user with ear-based headphones.
Key Applications
- •Sleep stimulation — delta wave amplification during SWS
- •Hearing aids — for conductive hearing loss
- •Low arousal — skull transmission is less likely to cause startle than air-conducted sound
Why does Bone Conduction matter?
Bone conduction matters because it lets sound reach the inner ear by vibrating the skull, bypassing the ear canal and middle ear. This is part of why your own voice sounds different on a recording: you normally hear it partly through bone.
It also has practical uses. Bone-conduction headphones leave the ear canal open so users stay aware of their surroundings, and bone-anchored hearing devices help some people whose outer or middle ear cannot pass sound normally.
How is Bone Conduction measured?
Bone conduction is measured during a standard hearing test with a small vibrator placed on the bone behind the ear or on the forehead. An audiologist compares bone-conduction thresholds with air-conduction thresholds measured through headphones. If hearing through air is worse than through bone, the problem likely lies in the outer or middle ear (conductive hearing loss). If both are reduced equally, the problem is more likely in the inner ear or auditory nerve (sensorineural hearing loss). Simple tuning-fork tests, such as the Weber and Rinne tests, use the same principle for quick bedside screening.
In ONDA Life
The Phase-Locked Sleep article covers bone conduction for acoustic deep sleep stimulation.