- The primary role of the auditory (Eustachian) tube is to equalize air pressure between the middle ear and the nasopharynx.
- This function is crucial for maintaining the proper pressure balance on both sides of the tympanic membrane (eardrum), which is essential for optimal vibration and transmission of sound.
- When there is a difference in pressure, such as during altitude changes in an airplane, the Eustachian tube opens to allow air to pass, thereby balancing the pressure and preventing discomfort or potential damage to the ear.

- While the Eustachian tube also helps in the drainage of middle ear secretions, its primary function remains the regulation of pressure. It does not directly participate in the transmission of sound vibrations—that role is fulfilled by the ossicles in the middle ear, nor does it serve as a barrier against infections, although its dysfunction can predispose to middle ear infections.

Key points:
- The Eustachian tube connects the middle ear to the nasopharynx.
- It functions mainly to equalize air pressure on both sides of the tympanic membrane.
- This pressure equalization is vital for proper hearing function and ear comfort.
- It occasionally allows drainage of secretions but this is a secondary role.

Reference: Katz, J. Audiology Diagnosis, Volume 1, Chapter 3 / Page 45