plasticity (n.)

A term used in PHONETICS referring to the scope for variation which exists in an individual’s VOCAL TRACT. The physical characteristics of the tract do not determine the acoustic characteristics of a person’s speech in an absolute way (as with fingerprints), but only the range within which a particular parameter is able to vary. For example, the length and mass of the VOCAL FOLDS will be a major factor in determining whether a speaker has a naturally CREAKY voice, but other factors will allow that speaker to avoid sounding so creaky – and also allow other speakers to assume a creaky voice in order to sound like him (as happens routinely with speech impressionists). The plastic nature of the speech mechanism is a major argument against the view that there are immutable cues to speaker identity in the speech signal.