This chapter describes various aspects of the human voice as a means of communication in speech and singing. From the point of view of function, vocal sounds can be regarded as the end result of a three stage process: (1) the compression of air in the respiratory system, which produces an exhalatory airstream, (2) the vibrating vocal folds’ transformation of this air stream to an intermittent or pulsating air stream, which is a complex tone, referred to as the voice source, and (3) the filtering of this complex tone in the vocal tract resonator. The main function of the respiratory system is to generate an overpressure of air under the glottis, or a subglottal pressure. Section 16.1 describes different aspects of the respiratory system of significance to speech and singing, including lung volume ranges, subglottal pressures, and how this pressure is affected by the ever-varying recoil forces. The complex tone generated when the air stream from the lungs passes the vibrating vocal folds can be varied in at least three dimensions: fundamental frequency, amplitude and spectrum. Section 16.2 describes how these properties of the voice source is affected by the subglottal pressure, the length and stiffness of the vocal folds and how firmly the vocal folds are adducted. Section 16.3 gives an account of the vocal tract filter, how its form determines the frequencies of its resonances, and Sect. 16.4 gives an account for how these resonance frequencies or formants shape the vocal sounds by imposing spectrum peaks separated by spectrum valleys, and how the frequencies of these peaks determine vowel and voice qualities. The remaining sections of the chapter describe various aspects of the acoustic signals used for vocal communication in speech and singing. The syllable structure is discussed in Sect. 16.5, the closely related aspects of rhythmicity and timing in speech and singing is described in Sect. 16.6, and pitch and rhythm aspects in Sect. 16.7. The impressive control of all these acoustic characteristics of vocal signals is discussed in Sect. 16.8, while Sect. 16.9 considers expressive aspects of vocal communication.
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