Condition 2, an inertive supraglottal
vocal tract air column, can also produce a direction-dependent force on the vocal folds.
In principle, the exceptional behaviour of the Estonian medial short /k/ may have its source in either glottal or in supraglottal
manoeuvres, or in a combination thereof.
Maddieson (1997) suggests that one of the factors which contribute to VOT differences is the relative size of the supraglottal
cavity behind the point of constriction.
In consonants produced with a complete closure, air pressure quickly builds up in the supraglottal
area behind the closure.
Furthermore, voicing of stops requires a difference between subglottal and supraglottal
pressure (in order to let the vocal folds vibrate), which is usually maintained by pharyngeal expansion and larynx lowering (Kent and Moll 1969; Perkell 1969; BellBerti 1975).
injection of botulinum toxin type A in adductor type spasmodic dysphonia with both intrinsic and extrinsic hyperfunction.
The upper portion of the vocal fold is spread apart, proportional to the steady pressure that is built up in the supraglottal
vocal tract, behind the semi-occlusion.
1983, Enlargement of the Supraglottal
Cavity and Its Relation to Stop Consonant Voicing.--The Journal of the Acoustical Society of America 73, 1322-1336.
One of the mezzo sopranos, MS1, demonstrated increased supraglottal
compression during the evaluation, which may have indicated a pattern of vocal hyperfunction.
A steady positive supraglottal
pressure [P.sub.2], which pushes against the upper surfaces, can mediate the usually greater pressure [P.sub.1] applied at the lower surfaces.
Titze suggested that timbre transitions (passaggi) can be voluntary, by regulating vocal fold adduction--or involuntary, created from resonances (subglottal sound waves affecting supraglottal
sound waves) within the trachea.
The corresponding supraglottal
vocal tracts for these formant-harmonic interactions were identified as a megaphone mouth shape for belt and an inverted megaphone mouth shape for operatic production in a comparable frequency range (around [A.sub.4]).