For conductive hearing loss:
The vibrations from the BCHD are passed into the skull, either through the skin, through a titanium abutment embedded in the bone, or via an vibrating implant. The vibrations cause the fluid in the inner ear (cochlea) to vibrate, which in turn causes the small inner ear hair cells to move, leading to the generation of an electrical impulse in the hearing nerve, which the brain perceives as sound.
Wearing a BCHD means that the ear canal is left open for air to circulate, unlike when wearing a conventional hearing aid which blocks the ear canal and can lead to problems with infections.
For single sided deafness
The vibrations from the BCHD placed on the skull behind the ear with hearing loss are transmitted across the skull and are perceived in the good ear. This means that the patient who will often miss things that are said on his/her poor hearing side now has an awareness of sounds on that side, albeit in the opposite ear.