What is the main function of the eardrum in the human ear?

The primary function of the eardrum, also known as the tympanic membrane, is to vibrate in response to sound waves. When sound waves enter the ear canal, they hit the eardrum, causing it to vibrate. These vibrations are then transferred to the bones of the middle ear (ossicles), which amplify and further transmit the sound to the inner ear. This mechanical process is critical for the conversion of sound energy into a format that the brain can interpret, which makes option B the correct answer.

While regulating pressure is a function related to the overall ear anatomy, especially involving the Eustachian tube, the eardrum itself does not perform this role. Transmitting signals to the brain is a function of the auditory nerve and the inner ear, which processes the vibrations from the eardrum into nerve signals. Lastly, filtering out background noise is primarily performed by the brain and not by the eardrum itself, which serves primarily as a barrier and a vibration mechanism for sound.