Introduction

Lexical tones are pitch patterns that serve to provide contrasts in word meaning. They perform this function analogously to segments such as voiced and voiceless stops, except that tone may extend beyond one segment. Mandarin Chinese phonemically distinguishes four tones, with tone 1 having high-level pitch, tone 2 high-rising pitch, tone 3 low-dipping pitch, and tone 4 high-falling pitch (Chao, 1948). The same segmental context carries different meanings depending on the tone. For example, the meaning of Mandarin Chinese ma with tone 1 is “mother,” the tone 2 version means “hemp,” and the tones 3 and 4 meanings are “horse” and “scold,” respectively.

Pitch or tone is a function of the rate of vocal fold vibration (see Ohala, 1978, for a review of tone production). As stipulated in the myoelastic–aerodynamic theory of vocal fold vibration (e.g. Van den Berg, 1958), it is a cyclic process that is achieved by a complex combination of aerostatic and aerodynamic forces, operating together with air flow and laryngeal muscle forces. Changes in fundamental frequency (or in rate of vocal fold vibration) are made by manipulating tension in the vocal folds. This tension is increased or decreased by the laryngeal muscles, particularly the cricothyroid muscle and the thyroarytenoids. The cricothyroid has been linked to both rises and falls in pitch, while sternohyoid activity is associated with pitch lowering (Sagart et al., 1986).

The rate of vocal fold vibration is quantified as the fundamental frequency (F0), expressed in Hertz (Hz).