By varying the tension on the vocal cords during voicing, and the forse of the passing stream of air, one can vary the ‘pitch’ and the ‘volume’. Different individuals have pitch ranges of from one to three octaves. English makes phonemic use of both pitch and volume, the former in its intonational system (4), the latter principally in its accentual system (5).
- Hockett (1958), Pag. 66