Summary figure illustrating the age ranges from a range of speech production studies.

Acoustic‐phonetic variability can be structured in a number of ways. Drawing from laboratory studies and natural settings, the panels depict four possible relationships between speech variability (using voice‐onset time as the example dimension) and nonspeech variability (using second‐formant frequency as the example dimension). Colors refer to speech‐sound category. Rugs indicate frequency of each value on each axis.