Bone Phone
Technology Review
July/August 1998 - page 19

Most devices designed to help the hard-of-hearing simply amplify sound. This
approach doesn't work well for people with severe defects in the outer or
middle ear. Daewoo Technologists of Lyndhurst, NJ has developed a telephone
that takes a different approach: sending vibrations directly to the inner ear
through the bones in the head. 

We hear mostly by "air conduction" with sounds traveling through the ear
canal and middle ear to the inner ear, where they are translated into nerve
impulses that go to the brain. But we also hear via "bone conduction", and
Daewoo's phone exploits this effect. A knob in the center of the earpiece is
pressed to a bony part of the head and transmits vibrations directly to the
inner ear. The phone's makers say the instrument could also be useful for
people with normal hearing who work in noisy environments such as
construction sites.