We normally hear sounds because they enter the outer ear and are transmitted to the organ of hearing in the inner ear, called the cochlea, via the middle ear, which contains the smallest bones in the body. The cochlea is itself embedded in hard bone and has fluid-filled chambers separated by a flexible partition called the basilar membrane. The fluid in these chambers is normally excited by the middle ear through a small opening, covered by a flexible membrane, called the oval window. Since the fluid in the cochlea cannot be compressed, this excitation of the oval window is normally matched by an equal and opposite motion of another opening, called the round window, which relieves the pressure in the cochlea. In some people, however, the bone surrounding the cochlea grows over the oval window, preventing its motion, and so causing significant hearing loss.
A recent paper (Royal Society Interface 11: 20131120) has shown that the ear can be excited even if the normal mechanism of sound transmission to the cochlea, though the middle ear and the oval window, is blocked. The acceleration of a tiny, electromagnetically driven, magnet placed directly on the round window was shown to effectively excite the cochlea at audio frequencies via the near field pressure generated in the fluid chambers close to the basilar membrane. The research was funded by the Medical Research Council and resulted from a collaboration between the Universities of Brighton, Dresden, Munich and Southampton. This work may enable the development of a new type of hearing aid for patients whose normal hearing in impaired by blockages of the oval window.