Transmitting sound via the bones in the skull to the inner ear. Bone conduction speakers rest against the side of the head near the ears, but not in them. Dating back to the 1920s, bone conduction has been used for hearing aids and is still used for people who cannot tolerate a device inserted in their ears.
Why You Think You Sound Different
When you speak, you hear your voice from your ears as well as the bone conduction in your head, which is lower pitched. When you hear your recorded voice, there is no bone conduction, and you sound higher pitched. See Bluetooth headset
and Google Glass
Bone Conduction in a Hat
Bone Conduction in the Pool
A pair of bone conduction speakers (top) are sewn into every Cynaps hat phone (bottom), allowing it to be put on and taken off like any other baseball cap. See Bluetooth headset
In order to swim laps to his favorite music, this man is wearing a Finis waterproof MP3 player that uses bone conduction speakers (one unit is on each side of his head).
Through the Head
Instead of sound waves entering the outer ear (top), the sound vibrates the bones in the head and reaches the inner ear (bottom). (Image courtesy of Cynaps bone conduction products, www.maxvirtual.com)