Sound waves are pressure variations in air that the cochlea decodes as electrical signals

Sound waves propagate by air molecules compressing and rarefying, creating regions of higher and lower pressure. These mechanical vibrations are transduced by the ear: the eardrum captures pressure variation, the tiny bones (ossicles) of the middle ear amplify it, and the fluid-filled cochlea converts it into electrical signals through the electrochemical triggering of hair cells by the motion of the basilar membrane. At the point where sound waves meet human audition, the domain of physics gives way to psychophysics, and then to cognitive psychology in the brain.

Examples

Underwater sound travels faster than in air because the medium is denser. An ADC converts a continuous pressure-derived voltage into digital samples, a useful analogy to the ear’s own transduction of pressure into neural signals.

Assessment

Name the sequence of physical media (air, bone, fluid) that a sound wave passes through before becoming an electrical signal in the human auditory system. At which point does the physical domain become psychophysical?