Final answer:
The external acoustic meatus directs sound waves to the tympanic membrane, which vibrates and sends these vibrations through the middle ear ossicles to the oval window and into the cochlea. The movement of the cochlea fluid excites hair cells, which translate these vibrations into electrical signals for the brain to perceive as sound.
Step-by-step explanation:
Sound waves that enter the external acoustic meatus cause the tympanic membrane to vibrate back and forth, reproducing the vibrations of the sound-wave source. The tympanic membrane, also called the eardrum, is a crucial part of the auditory system. When sound waves travel along the auditory canal, they strike the tympanic membrane, causing it to vibrate. These vibrations are then transmitted through the middle ear via the three ossicles: the malleus, incus, and stapes. The stapes connects to the oval window, which is a membrane leading into the cochlea of the inner ear.
This motion then causes fluid inside the cochlea to move, stimulating the hair cells located on the basilar membrane. The basilar membrane's movements correspond to the sound waves' frequency and amplitude, transforming these mechanical vibrations into nerve impulses that the brain interprets as sound. The entire process from the vibration of the tympanic membrane to the activation of the receptors on hair cells is crucial for hearing.