In principal the function of peripheral hearing is to convert sounds (air pressure differences) into electrical signals which the brain can interpret. The ears are catching sounds and funnelling them into the ear canal. Due to their location on either sides of the head and their forward facing, sounds from the front are received louder than from the rear (loudness difference) and sounds reach one ear before the other (time difference). Due to the difference shape the ear gives an individual “colour” to each sound. Surface difference of the ear and the ear canal entrance causes the sound to get amplified.
The ear canal due to its shape accentuates sounds in the 2-4,000 Hz range which is very important for speech understanding.
At the end of the ear canal is the eardrum, which starts to vibrate when hit by the sound waves.
Attached to the eardrum is a serious of 3 tiny bones, which, as the eardrum vibrates vibrate along with it.
The last of these bones, the stapes, moves in and out of a liquid filled cavity in the scull called the cochlear. The cochlea is filled with thousands of tiny, so called haircells, which when stimulated elicit an electrical impulse. These haircells are connected to strands of the hearing nerve which conduct the electrical signal to the brain.
The Cochlear, Pitch & Frequency
The cochlea is central to our hearing, converting mechanical energy into electrical stimulation.
When the stapes moves in and out of the cochlear it produces waves in the liquid. Depending on the frequency of these waves hair cells in a certain area of the cochlea will respond by producing electricity. This is how peripheral hearing resolves frequency/pitch.
The louder a sound is, the stronger the wave in the liquid will be and the more haircells in a certain area will be stimulated. The more haircells are simulated the louder we will ultimately perceive a certain frequency/pitch.