Phonation and resonance; formants; vowels

Lloyd Hanson wrote:

I have long held and taught that resonance factors have so strong an effect
on vocal phonation that resonance can and does alter the position of
registration events by as much as a minor third for closed vowels as
compared to open vowels. Consequently, when I give registration pitch
ranges it is always for the vowel [a].

Research by Donald Miller (no relation to Richard Miller, that I know of)
delves into the effect of resonance on phonational tone and explains the
phenomenon by defining which of the phonated partials is emphasized by the
resonance attributes of the vocal tract. Because the vocal tract is
adjustable, the singer can, in many instances, make adjustments such that a
different phonated partial is affected which, in turn, will change the
tonal color of the voice in a very dramatic manner.

For example, male call voice which occurs in most untrained singers in their
passaggio area can be altered to become a ringing covered tone by lowering
the resonance attribute of the vocal tract through lowering the larynx.
This is exactly what males have done for centuries as they learn to
negotiate from chest voice into head voice in the passaggio area. And it
us usually called cover. Donald Miller's research explains why this
happens and givs us much better clues about how to train male voices to
achieve this desirable ability.

But the primary phenomenon that occurs is an alteration of phonated tone by
the vocal tract which is selectively emphasizing one phonated partial over
another. This kind of alteration of the vocal tract to effect phonated
tone is also what occurs when we change from one vowel to another. Vocal
tract alterations are, therefore, used to produce all vowels and to alter
slightly any given vowel.

Johan Sundberg says:

The vocal tract resonator has different requirements for the sounds that try to pass through it, depending upon the frequency of that sound. Certain frequencies pass through the resonator easily and, as a consequence, are given a high amplitude....In the vocal tract these resonances are called formants. They and they alone determine vowel quality and donate personal timbre to the voice. Vowel color is determined by the two lowest formants; timbre is determined by the third, fourth, and fifth formants. Tuning the formant frequencies is done by changing the shape of the vocal tract: the jaw, the tongue, the lip opening, the larynx, and the side walls of the pharynx. Adult females have shorter vocal tracts than adult males. Therefore their formant frequencies are 15% higher on average than those of the adult male.

∙ Adjusting the shape of the vocal tract is the most common
method for tuning the formant frequencies.
∙ The first formant is responsive to the jaw opening.
∙ The second formant responds to the tongue shape.
∙ The third formant is responsive to the position of the tip
of the tongue and to the size of the cavity between the
lower teeth and the tongue.
∙ The fourth and fifth formants are more difficult to control by
these means.