Which membrane separates the external ear from the middle ear and vibrates in response to sound waves?

Which membrane separates the external ear from the middle ear and vibrates in response to sound waves?

• A. Oval window.
• B. Cochlea.
• C. Eustachian tube.
• D. Tympanic membrane (eardrum).

Answer: (D)

Sound waves are converted into mechanical vibrations at a boundary membrane between the outer and middle ear. When air pressure changes strike this thin, taut membrane, it vibrates, turning acoustic energy into motion that can be passed on to the middle-ear bones. This membrane marks the separation between the external ear and middle ear, so its vibration is the first step in the chain that transmits sound inward. The oval window, by contrast, is the boundary between the middle ear and inner ear and responds to the movement of the middle-ear bones, not to direct sound from the outside. The cochlea is part of the inner ear and contains sensory receptors, while the Eustachian tube helps equalize pressure rather than participate in vibration. Therefore, this boundary membrane is the eardrum.

Sound waves are converted into mechanical vibrations at a boundary membrane between the outer and middle ear. When air pressure changes strike this thin, taut membrane, it vibrates, turning acoustic energy into motion that can be passed on to the middle-ear bones. This membrane marks the separation between the external ear and middle ear, so its vibration is the first step in the chain that transmits sound inward. The oval window, by contrast, is the boundary between the middle ear and inner ear and responds to the movement of the middle-ear bones, not to direct sound from the outside. The cochlea is part of the inner ear and contains sensory receptors, while the Eustachian tube helps equalize pressure rather than participate in vibration. Therefore, this boundary membrane is the eardrum.