Our ears allow us to detect sounds, which pass through the air as waves of varying pressure. On reaching the ear, the waves travel through several structures to the cochlea in the inner ear. There, receptor cells produce signals that go to the brain. The human ear can detect sounds over a very wide range of pitch and loudness, from the high-pitched squeaks of a mouse to the roar of a passenger jet.
The outer ear channels sound waves into the ear canal. These sound waves cause the eardrum, a thin membrane at the end of the ear canal, to vibrate. The vibrations are transmitted via three tiny bones in the middle ear to the cochlea in the inner ear.
Inside the cochlea, sound vibrations make these sensory hairs move, which triggers signals in attached receptor cells. The signals pass to the brain, which works out the pitch and loudness of the sound.