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Mechanisms Of Acoustic Perception

The middle ear is the hollowed air-filled space surrounded by small bones in the temporal bone of the skull just behind the ear drum. This same area is also referred to as the tympanic cavity. What separates this area from the outer ear is simpl the ear drum. In the tympanic cavity there are three tiny bones that vibrate when exposed to sound waves. These three bones are titled the malleus, which is also known as the hammer, the incus, which is also referred to as the anvil, and then there is the stapes, the stapes is also known commonly as the stirrup.
          These bones form a type of chain around the middle ear basically and stretch to the oval window of the inner ear. Their overall main function is to amplify sound by transferring acoustic energy from compression waves in the air, into fluid-membrane waves within the cochlea.
          The movement of these small bones can be stiffened by two muscles, the stapedius, and tensor tympani which are under the control of the facial nerve and trigeminal nerve. These muscles contract in response to loud sounds which ultimately reduce the transmission of sound to the inner ear. This is referred to as the acoustic reflex.
          The middle ear connects to the back of the throat and nose by means of the Eustachian tube. The Eustachian tube is auditory openings that we open when we yawn and swallow.
The middle ear is hollow accordingly, if moved to high-altitude environments, or dives into the water, there will be a pressure difference between middle ear and that outside environment. This pressure will create risk of bursting or ultimatley damaging the tympanum if not relieved. This is one of the functions of the Eustachian tubes which connect the middle ear to the nasopharynx. The Eustachian tubes are usually closed off at the nose end to prevent being clogged with mucus, but they can be opened by lowering and protruding the jaw; this is why yawning relieves pressure felt in the ears when aboard an aircraft.