We say magic! Although the sound engineers would say that bone conduction works by harmlessly conducting sound to the inner ear through the bones of the skull. Specifically designed transducers produce acoustic waves that are directly perceived by the cochlea, thus liberating the outer ear. The resulting sound feels genuinely different to any other conventional audio experience. The technology was first used in the military so that soldiers could communicate with each-other whilst still having their ears open to their surroundings, and then by people with a variety of hearing conditions. Now it has evolved into wider use by adventurous individuals looking to have a uniquely liberating experience.