Tongue and lip constriction locations systematically shift formant frequencies from neutral values

Evidence

A commonly referenced set of average formant frequency values for men, women and children for a number of vowels, taken from Peterson and Barney (1952), is shown in Table 4.3. Formant frequency values for these vowels can be predicted with reference to their articulation. For example, the vowel in beat has a constriction toward the front of the tongue in the region of both N2 and N3 (see Figure 4.38), and reference to Figure 4.39 suggests that F1 is lowered in frequency, and F2 and F3 are raised from the values one would expect for the neutral vowel. The vowel in part, on the other hand, has a significant constriction in the region of both A2 and A3 (see Figure 4.38), resulting in a raising of F1 and a lowering of both F2 and F3 from their neutral vowel values. The vowel in boot has a constriction at the lips, which are also rounded so as to extend the length of the vocal tract, and thus all formant frequencies are lowered from their neutral vowel values. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1349

Categorization

• DEFINE: This clarifies that formants (F1-F3) are directly predicted by articulation geometry, linking acoustic output to physical tongue and lip position.
• corroborated: 2 independent passages support this claim — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1349
• XREF: connects to: Sonograms visually expose vowel formants as enhanced frequency bands