How does the external auditory canal enhance certain sound frequencies?

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Cross-section diagram of the human ear showing the outer ear, middle ear, and inner ear, with labeled parts including the auricle, auditory canal, tympanic membrane, ossicles, cochlea, semicircular canals, and nerves. — human ear Structure of the human ear.

The external auditory canal enhances sound through a process of resonance. Because of its physical dimensions, the canal acts as a resonator that amplifies sounds with relatively short wavelengths, specifically those in the frequency range between 2,000 and 7,000 hertz.1

This resonance enhancement is significant because it helps determine the frequencies to which the human ear is most sensitive, which are the frequencies essential for distinguishing the sounds of consonants. By funneling sound waves toward the tympanic membrane, the external auditory canal ensures that these important sound frequencies reach the eardrum with increased intensity.1