More about Hearing

HOW DOES SOUND OCCUR
Sound is created when the air is subjected to a time-varying (oscillating) disturbance – such as due to the vibrations from vocal cords, or the pounding of a piece of machinery, or anything that vibrates. The oscillations (actually the compressions and rare factions of the air molecules) spread outward through the air from the sound source.  The external ear (pinna and earcanal) intercepts these sound waves.  They pass along the earcanal to the eardrum, through the middle ear to the cochlea of the inner ear.  The cochlea contains thousands of tiny hair cells bathed in fluid.  The fluid is set into motion by the vibrations and in turn this moves the hair cells, which is then translated into nerve impulses that are transmitted to the brain.  The waves are interpreted, i.e. heard as sound.