Implants for bone-conducted hearing and active middle ear implants transfer information about sound and speech to middle ear in the form of vibrations. Vibrations quiver inner ear fluids, stimulate the hair cells and evoke the sound percepts.
That is how they differ from cochlear implants, which stimulate nervous structures by electric impulses. The implant for bone-conducted hearing transfers vibrations into the skull bones, whereas the active middle ear implant transfers the vibrations aiming at midle ear structure (middle ear ossicles, oval window membrane).