Page 119 - The Master Handbook Of Acoustics

94 CHAPTER FIVE

Vocal
Sound Speech
source tract sounds
shaping
A

Vocal
cord
vibration

Vocal
Constriction tract Speech
turbulence sounds
shaping

Plosive

B
FIGURE 5-3
(A) The human voice is produced through the interaction of two essentially inde-
pendent functions, a sound source and a time-varying-filter action of the vocal tract.
(B) The sound source can be broken down into vocal-cord vibration for voiced sounds,
the fricative sounds resulting from air turbulence, and the plosive sounds.

nasal cavity) and varies from zero to about 3 sq in (20 sq cm). The nasal
cavity is about 4.7 in (12 cm) long and has a volume of about 3.7 cu in
(60 cu cm). These dimensions are mentioned because they have a bear-
ing on the resonances of the vocal tract and their effect on speech
sounds.

Formation of Voiced Sounds

If the symbolic boxes of Fig. 5-3 are elaborated into source spectra and
modulating functions, we arrive at something everyone in audio is
interested in—the spectral distribution of energy in the voice. We also
get a better understanding of the aspects of voice sounds that contribute
to the intelligibility of speech in reverberation, noise, etc. Figure 5-4
shows the steps in producing voiced sounds. First, there is the sound