Slide show: How you hear

The middle ear contains three tiny bones:

• Hammer (malleus) — attached to the eardrum
• Anvil (incus) — in the middle of the chain of bones
• Stirrup (stapes) — attached to the membrane-covered opening that connects the middle ear with the inner ear (oval window)

The vibration of the eardrum triggers a chain of vibrations through the bones. Because of differences in the size, shape and position of the three bones, the force of the vibration increases by the time it reaches the inner ear. This increase in force is necessary to transfer the energy of the sound wave to the fluid of the inner ear.