tympanic membrane or eardrum

a membrane that separates the outer ear from the middle ear. The eardrum vibrates in response to sound waves and passes the vibrations on to the bones of the middle ear.

Hearing in Land Mammals
DOSITS Videos
Blast Injury, Barotrauma, and Acoustic Trauma
Hearing in Amphibious Marine Mammals
Hearing in Cetaceans and Sirenians, the Fully Aquatic Ear
Media Backgrounder
Tutorial: Can Animals Sense These Sounds Part I
How do aquatic birds hear?
Low Frequency Sound Production and Reception in Mammals