Page 108 - Master Handbook of Acoustics
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FIGURE 5-4 The production of voiced sounds can be considered as several steps. (A) Sound is first
produced by the vibration of the vocal cords; these are pulses of sound with a spectrum that falls off
with frequency. (B) The sounds of the vocal cords pass through the vocal tract, which acts as a time-
varying filter. Acoustical resonances, called formants, are characteristic of the vocal pipe. (C) The
output voiced sounds of speech are shaped by the resonances of the vocal tract.
Formation of Unvoiced Sounds
Unvoiced sounds are shaped as shown in Fig. 5-5. Their production is similar to that of voiced
sounds. Unvoiced sounds start with the distributed, random-noise–like spectrum of the turbulent air as
fricative sounds are produced. The distributed spectrum of Fig. 5-5A is generated near the mouth end
of the vocal tract, rather than the vocal cord end; hence the resonances of Fig. 5-5B are of a somewhat
different shape. Figure 5-5C shows the sound output shaped by the time-varying filter action of Fig. 5-
5B.
FIGURE 5-5 A diagram of the production of unvoiced fricative sounds such as f, s, v, and z. (A) The
