“Hearing” truly begins when sound waves pass through the ear canal and reach the eardrum. Our bodies receive and process sound in three different stages: the signal of a specific sound travels into the outer ear (eardrum), is transcribed by the middle ear (ossicles), and is broadcast to the inner ear (cochlea) where it passes on to the brain.
Once sound waves reach the eardrum, a delicate set of organs and bones get to work. These pieces function similarly to a stopwatch or even a computer hard drive, with a dozen different minuscule components working in tandem over the course of a microsecond.
As each sound wave reaches the outer ear, it causes the eardrum to vibrate like a strummed rubber band. This movement shifts then three tiny bones — the smallest in the human body, in fact — which amplifies those vibrations as they pass on to the cochlea.
The cochlea, which has a shape similar to a nautilus shell, is lined with tiny hairs. And as the sound vibrations reach different sections of the cochlea, these hairs — called stereocilia — move up and town. That, in turn, opens up pores that release neurotransmitters into a nerve connecting the cochlea to the brain.
Finally, those chemicals travel along the auditory nerve and are received, processed, and recognized by the brain as specific sounds. All of that happens at near-instantaneous speeds every millisecond of every day, regardless of whether we are awake or asleep.Sound signals affect many sections of the brain, but each area reacts differently based on how the brain categorizes the auditory signal. Music in particular takes full advantage of that process by generating a wide variety of mental, emotional, and physical reactions. And it is that variety that makes the psychology of music a focal point for many scientific studies.