Perceptual Coherence : Hearing and Seeing

346 Perceptual Coherence
Cross Section of
Vocal Tract
Nasal Cavity
Tongue
Teeth
Lips
Model of Vocal Tract
(A) i as in “Feet”
Throat
Back of Mouth
Mouth
(B) a as in “Father”
Back of Mouth
Throat
(C) u as in “Boot”
Mouth
Back of Mouth
Throat
Mouth
Acoustic Spectrum
40
Second Formant
= 2300 Hz
First
20 Formant
= 300 Hz
possible. Traditionally, the cardinal vowels have been thought to underlie
speaker normalization. Listeners use those vowels to correct for speaker
differences due to the size of the vocal tract, speaking rate, accent and
dialect, and so on. But in all likelihood, vowels are not recognized by the
frequencies of their resonances but by the ongoing speech signal that is
Lips
Lips
Decibels
0
−20
0 2000 4000
40
100
First Formant = 750 Hz
20
0
Se
Second Formant
= 1200 Hz
−20
0 2000 4000
20
0
−20
First Formant
= 350 Hz
Second Formant
= 800 Hz
−40
0 2000 4000
Frequency (Hz)
Figure 8.3. The articulatory process: the positions of the tongue, lips, teeth, and
jaw create the resonant cavities that create the resonances of the vocal tract. Those
resonances can be calculated on the basis of the size and shape of the cavities, and
the theoretical acoustic spectrum for each vowel is shown in the right column.
Adapted from Language and Communication, by G. A. Miller, 1981, San Francisco:
Freeman.
100
10
1
.1
10
1
.1
10
1
.1
.01
Amplitude Ratio