Final answer:
The contraction and expansion of the outer hair cells in the organ of Corti fine tune incoming sound waves.
Step-by-step explanation:
The contraction and expansion of the outer hair cells in the organ of Corti in the inner ear function to fine tune incoming sound waves. The longer stereocilia of the outer hair cells attach to the tectorial membrane, and when sound waves produce fluid waves inside the cochlea, these hair cells respond by bending, opening ion channels and depolarizing the hair cell membrane. This triggers nerve impulses that travel to the brain through the auditory nerve.