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How does the ear distinguish different speech sounds?

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Uncover the science behind the transformation of sounds into speech — speech Speech is the faculty of producing articulated sounds, which, when blended together, form language.

The ear distinguishes different speech sounds through a complex process of mechanical analysis and neural transmission. Within the cochlea, sound vibrations cause the basilar membrane to vibrate at specific locations depending on the frequency, a process known as "place theory." High-frequency sounds stimulate the basal end, while low-frequency sounds stimulate the apical end.1

These vibrations trigger hair cells in the organ of Corti, which convert mechanical energy into electrical impulses sent to the brain via the auditory nerve. Speech sounds are further defined by acoustic factors such as formant frequencies, which characterize the shape of the vocal tract, and the fundamental frequency, which relates to pitch.123

While lower levels of the auditory pathway process basic properties like pitch and loudness, the cerebral cortex is essential for analyzing complex stimuli like speech, where the temporal sequence of sounds is critical. Infants are born with a universal sensitivity to phonemes, the contrasting elements that distinguish words, though this sensitivity narrows as they adapt to their native language.456