<prompt> The effective diameter of the tympanic membrane is25 mm230 mm240 mm245 mm2  <response>: Effective diameter or vibratory area of tympanic membrane is 45mm2; Area of tympanic membrane is 90mm2 Stapes footplate area is 3.2mm2 Ref: PL Dhingra 6th edition of Ear, Nose and Throat; pg no 15 