When the eardrum is moved inward due to sound vibrations, transferred through the outer ear, it transmits to the handle or manubrium of the malleus which is connected to the ear drum.

The manubrium of the malleus is firmly attached to the medial surface of the membrane as far as its center, which it draws toward the tympanic cavity; the lateral surface of the membrane is thus concave, and the most depressed part of this concavity is named the umbo.