The human ear works like a relay team, with each runner carrying the baton along one leg, and then passing to on to the next, until finally crossing the finish line!
First, a sound from the environment is picked up by the outer ear (aka pinna) and passed down the ear canal to the eardrum.
Second, the eardrum begins to vibrate, which causes the chain of three tiny ear bones (hammer, anvil, and stirrup) in the middle ear to move.
Third, the movement from the chain of ear bones sends the vibration from the eardrum to the inner ear (aka cochlea).
Fourth, when the sound vibration hits the inner ear it becomes a fluid wave, which travels along to stimulate the nerve endings (aka hair cells) of the high pitches or low pitches, depending on the frequency of the original sound.
Finally, the stimulated nerve endings send the sound information along the auditory nerve to our brain where the sound is perceived and interpreted.