Retrospectacle has a great beginner’s guide to hearing for anyone interested in how sound waves get converted into neural impulses for the brain.
The article describes the wonderful mechanics of the ear. It’s quite striking how much the physical make-up of the ear filters and ‘processes’ the sound waves before they even reach the sensory cells that connect with the nervous system.
All the hair cells sit on top of a firm but flexible membrane called the basilar membrane. As the stapes bangs against the oval window, a wave is transmitted through the basilar membrane. The distance this wave travels (and subsequently, the hair cells that are stimulated) are dictated by the frequency of the sound wave. The basilar membrane becomes stiffer at the top of the cochlea, which allows different parts of the cochlea to correspond to specific frequencies. High frequency sound-specifity corresponds to the base of the cochlea while the top (or “apex”) of the cochlea transduces low frequency sounds. The area on the cochlea where the most hair cells are stimulated during a given sound wave is considered the resonance point, and loudness can be perceived by the number and duration of hair cell stimulation at that point.
The article is both informative and wonderfully illustrated for those wanting to get a grip on one of our most interesting senses.
Link to Retrospectacle on ‘Basic Concepts: Hearing’.