The term tympanum is composed of two words: EARDRUM and DRUM. An EARDRUM, also known as a tympanic membrane, is a thin membrane that separates the outer ear from the middle ear and vibrates when sound waves enter the ear. A DRUM is a percussion instrument consisting of a hollow cylinder or cone-shaped shell that is struck with sticks or hands to produce a sound. The tympanum is the combination of these two words and refers to the EARDRUM, which acts like a DRUM when it vibrates in response to sound waves.