Tympanum
in anatomy, the drum, middle ear, or middle chamber of the ear; a narrow, irregular cavity in the substance of the temporal bone, placed between the inner end of the external auditory canal and the labyrinth. Its roof is formed by a thin plate of bone, situated on the upper surface of the petrous bone, its floor is a narrow space, its outer wall is formed mainly by a thin semi-transparent membrane-the membrana tympani-which closes the inner end of the external auditory meatus; its inner wall is uneven, its anterior extremity is narrowed by the gradual descent of the roof, and is continued into the Eustachian orifice, and its posterior one has at its upper part a large, and several small openings leading into the mastoid cells. The tympanum receives the atmospheric air from the pharynx through the Eustachian tube, and contains a chain of small bones by means of which the vibrations communicated from without to the membrana tympani are in part conveyed across the cavity to the sentient part of the internal ear.
In machinery, a kind of hollow treadwheel wherein two or more persons walk, in order to turn it, and thus gave motion to a machine. In music, a hand-drum or tambourine, but covered with parchment back and front. It was used in conjunction with various kinds of harps, lyres, and pipes, cymbals of metal, the straight brass trumpet and curved brass horn, the castanets of wood and metal.