The ear comprises three parts—the outer ear, middle ear, and inner ear—which work together to enable hearing. Following the outer ear's role in collecting and initially processing sound, this section focuses on the middle ear.

The middle ear is a small, air-filled cavity within the temporal bone, with a volume of approximately 1-2 cm³. Its primary function is to efficiently transfer the acoustic vibrations received from the tympanic membrane—which are transmitted through air—into the fluid-filled environment of the inner ear. A key challenge it overcomes is the significant loss of sound energy that occurs when sound waves pass from air to fluid, as most energy would normally be reflected. The middle ear solves this impedance-matching problem.

The main components of the middle ear work in concert as follows:

• ​Tympanic Membrane (Eardrum):​​ This thin (approx. 0.1 mm), semi-transparent membrane marks the entrance to the middle ear. It vibrates in response to sound waves and transmits these vibrations to the ossicular chain.

• ​Ossicular Chain:​​ This chain consists of the three smallest bones in the human body: the malleus (hammer), incus (anvil), and stapes (stirrup). They are connected by joints to form a lever system. The length ratio of the malleus handle to the long process of the incus is approximately 1.3:1, creating a lever effect that increases the force, amplifying sound pressure about 1.3 times. Furthermore, the effective vibratory area of the tympanic membrane (approx. 85 mm²) is significantly larger than the footplate area of the stapes (approx. 3.2 mm²). This area difference focuses the force onto a smaller surface, resulting in a substantial increase in pressure (amplification of approx. 17 times). Combined, these two mechanisms—the lever effect and the area ratio—boost the sound pressure by nearly 30 dB, effectively compensating for the energy loss that would otherwise occur at the air-fluid interface.

• ​Auditory Tube (Eustachian Tube):​​ This tube connects the middle ear cavity (tympanic cavity) to the nasopharynx. It is approximately 3.5-4.0 cm long in adults and functions to equalize air pressure on both sides of the tympanic membrane, which is essential for its free and optimal vibration. The auditory tube is shorter, wider, and more horizontal in children, making them more susceptible to middle ear infections (otitis media) following upper respiratory infections.

• ​Acoustic Reflex (Attenuation Reflex):​​ The middle ear contains two muscles: the tensor tympani and the stapedius muscle. In response to loud sounds, these muscles contract reflexively. This contraction stiffens the ossicular chain, reducing the transmission of loud vibrations and providing a protective, dampening effect for the delicate inner ear structures against acute acoustic trauma.