The Technique of Plastic Operations on the Sound Conducting Apparatus

HEARING depends on a greater proportion of the energy of incoming sound being transmitted through one of the windows of the internal ear, thus setting up a wave of increased pressure in the corresponding compartment of the perilymph space of the cochlea. Movement of the basilar membrane takes place with resulting movement of the perilymph in the other compartment and this is only possible if both windows are free. _In the normal ear a greater proportion of energy is transmitted through the chain of ossicles and the oval window, than that which is carried across the air in the tympanic cavity to the round window (Fig. i). Sound energy is lost during the transference from the tympanic membrane to the air in the middle ear and again from the air to the membrane of the round window. Pressure on the perilymph in the scala vestibuli is, therefore, greater than that on the scala tympani causing movement of the basilar membrane and the sensation of hearing (Fig. ia).