Auditory Phonetics
Auditory phonetics studies how listeners receive and interpret the speech signal — from the mechanics of the ear to the neural and cognitive processes that turn an acoustic stream into recognisable linguistic units. It is the least developed of the three branches of Phonetics, because perception is harder to measure directly than articulation or the acoustic signal.
The auditory pathway
Sound waves enter the outer ear and travel down the auditory canal to the tympanic membrane (eardrum), which vibrates and transmits motion through the three middle-ear ossicles — malleus, incus, stapes — to the oval window of the cochlea. Inside the fluid-filled cochlea, the basilar membrane responds tonotopically: high frequencies displace it near the base, low frequencies near the apex. Hair cells along its length transduce mechanical motion into neural signals carried by the auditory nerve to the brainstem and ultimately to auditory cortex.
Categorical perception
A central finding of auditory phonetics is categorical perception: listeners hear continuous acoustic differences as discrete phonemic categories. In classic experiments on voice-onset time, stimuli varying continuously between [b] and [p] are heard as either one or the other, with a sharp boundary rather than a gradient. Speakers of different languages place the boundary in different places, evidence that perception is shaped by the phonemic system of the listener's language.
Speech perception in non-native listeners
Adult learners' pronunciation difficulties often have a perceptual root: if a learner cannot reliably hear the contrast between two phonemes — Japanese /r/ and /l/, Vietnamese final /s/ and /z/ — production work alone yields slow gains. Perceptual training tasks, such as identification and discrimination of minimal pairs, are grounded in auditory phonetics and feed directly into ELT pronunciation methodology.