ABSTRACT
That vowels are very variable objects in articulatory and acoustic terms is a basic fact of phonetics. Even in the most highly-controlled speech productions elicited from phonetically trained speakers in optimal laboratory conditions, vowels vary in ways the speaker did not intend. As is made clear in other chapters in this volume, these differences result from variation in parameters such as speaking rate, the influence of neighboring consonants, and vowel-to-vowel coarticulation. The tongue executes articulations in rapid succession during speech production, and its movements must be finely coordinated with movements of the lips, velum, larynx, and jaw. Given the limits on the precision of our motor skills it is unsurprising that we cannot achieve exactly the same vowel quality each time we utter a vowel.
