Introduction to Acoustics

690 Part E Music, Speech, Electroacoustics
Part E 16.4
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Fig. 16.30 Role of the tongue tip and blade in tuning F3. As the tongue is raised to produce the retroflex configuration
required for the Swedish [ÖÔ] sound an acoustically significant volume is created under the tongue blade. Simulations using
APEX indicate that this cavity is responsible for the considerable lowering of the third formant associated with the [ÖÔ]
Figure 16.29 plots results from APEX simulation
experiments. It demonstrates how F1, F2 and F3 vary
in response to the tongue moving continuously between
palatal, velar and pharyngeal locations and maintaining
a minimum constriction area Amin of 0.25 cm 2 ,a7mm
jaw opening and keeping the larynx height constant.
The dashed and solid lines refer to rounded and spread
conditions. The calculations included a correction for
the impedance of the vocal tract walls ([16.54], [16.28,
p. 158]).
It is seen that the tongue movement has strong effect
on F2. As the constriction becomes more posterior
F2 decreases and F1 rises. In general, rounding lowers
formants by varying degrees that depends on the
formant-cavity relations that apply to the articulation
in question. However, for the most palatal position in
Fig. 16.29 – an articulation similar to an [�] oran[Ý], it
has little effect on F2 whereas F3 is affected strongly.
The F2 versus F1 plot of the lower diagram of
Fig. 16.29 was drawn to illustrate the effect of varying
the jaw. The thin lines show how, at various degrees of
jaw opening (6, 7, 8, 9, 12, 15, 19 and 23 mm), the tongue
moves between palatal and pharyngeal constrictions by
way of the neutral tongue shape. The bold lines pertain
to fixed palatal, neutral or pharyngeal tongue contours.
We note that increasing the jaw opening while keeping
the tongue configuration constant shifts F1 upward.
Figure 16.30 exemplifies the role of the tongue tip
and blade in tuning F3. The data come from an X-ray
study with synchronized sound [16.79,85]. At the center
r
a spectrogram of the syllable “par” [Ô�� Ö]. Perhaps
the most striking feature of the formant pattern is the
extensive lowering of F3 and F4 into the [ÖÔ].
The articulatory correlates are illustrated in the tracings.
As we compare the profiles for [� ]and[ÖÔ], we
see that the major change is the raising of the tongue
blade for [ÖÔ] and the emergence of a significant cavity
in front of, and below, the tongue blade. Simulations us-
Third formant
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formant
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First formant
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Fig. 16.31 The acoustic vowel space: possible vowel formant
combinations according to the APEX model
a