Dear Mike and Vocalisters:
You wrote:
> so, are you saying that the events in the vocal tract have a 'back
>pressure' effect on the vocal folds? and is this air or, sound or, both?
>obviously, different consonants create different degrees of resistance, in
>regard to air pressure, that must affect the folds, noticeably or not ( M and
>B for example). but do the vowels have the same effect or, do they have a
>different effect?
COMMENT: Yes, events in the vocal tract do have a 'back pressure',
as it were, on the vocal folds. But I am not referring to the
obvious increase in air pressure above the vocal folds that is found
in compressed consonants such as /m/ or /b/. I am referring to the
pressure above the vocal folds that occurs in the vocal tract during
the singing of vowels.
Sound is transmitted in air primarily through a wave action, not
through the movement of air in a single direction. It is often
assumed that the phonated sound is carried out of the mouth and into
space through the flow of breath. In fact, it is common for singers
and teachers of singing to use terms such as "let the breath carry
the tone" etc. But this is not how sound is transmitted. The flow
of breath hass little if any effect on the transmission of sound once
it is created at the vocal folds.
The primary function of the breath flow is to create an oscillation
of the vocal folds. The oscillation of the folds (vibration) creates
an alternating air pressure, or sound wave, in the vocal tract. As
with all sound transmission, the alternating air pressure radiates
outward in ever expanding "rings" much as one can observe from the
effect of dropping a stone into a quiet pool of water. A wave
transmission occurs because the molecules of the transmitting medium
(air or water in these cases) move away from the vibration source as
the energy of the vibration reaches them and then are drawn back
toward the source after the energy has passed . The molecules of the
medium do not move in a single direction but, rather, in a back and
forth motion until the energy that is being passed by their motion is
dissipated and moves outward to the next area of the medium.
Of course this is primary wave transmission knowledge badly
explained. It is information that you already know. But I have
found it constantly necessary to remind singers of this process
because it removes some misconceptions that are obstructive to an
understanding of how vocal resonance functions.
When the vocal tract is adjusted correctly for a given phonated pitch it will:
1 resonate the fundamental of that pitch or one of its
partials. If the pitch is "A", and the vocal tract is adjusted to
resonate "A", the vocal tract will increase the volume (amplitude) of
the phonated pitch and act as an acoustic amplifier. However, if
the vocal tract is tuned to a pitch that is not part of the "A"
overtone series (A, C#, E etc) the vocal tract will not increase the
amplitude of the phonated pitch but, instead, will act as a kind of
dampening agent on the phonated sound. The tone will be reduced in
amplitude and have "muffled" quality.
1 resonate two partials of the phonated pitch which are used by
the listener's ear to define the particular vowel that is selected.by
the singer. The choice of vowel is rather critical in this
condition. Not all vowels can be resonated with maximum efficiency
on all pitches. Because each vowel has its own two identifying
partials (vowel formants) it can be seen that these partials must be
found in the fundamental or partials of the phonated pitch if they
are to be present to be heard by the listener. Without their
presence the selected vowel will not be clearly identified and the
tone will lack luster for that particular vowel.
3 resonate a most important partial in the 2800 to 3200 Hrz
range which has become known as the singers formant. It is the
partial that must be present if the singer is to have his/her voice
carry well in a large hall or over an orchestra. This partial is not
necessary if the voice is amplified because the amplification çan
emphasize the spectrum of partials below pitch range of the singer's
formant enough to make the singer heard. This is one of the primary
reasons for the confusion between amplified singer's and
non-amplified singers about vocal technique. The non-amplified
singer must create the singer's formant if he/she is to heard
acoustically and this requires a quite different adjustment of the
vocal tract.
What has all this to do with "standing waves"? When the vocal tract
is adjusted correctly a complete wave or series of complete waves are
established in the vocal tract. These waves are maintained for the
duration of the pitch and vowel and provide an acoustic cushion or
acoustic spring immediately above the vocal folds. The vocal folds
benefit from this acoustic cushion because they do not have to rely
completely on their own muscular elasticity to return to a central
median position during phonation. The singer senses this as a
greater ease in singing. When a singer finds the correct "tuning" of
the vocal tract, as per above, he/she will often exclaim that it is
"too easy".
A too long explanation and, as is often said, more than needed. But
I am hesitant to write too little because it must assume knowledge
that I am reasonably sure not all of the Vocalister have or share.
Thanks for your question.
--
Lloyd W. Hanson, DMA
Professor of Voice and Vocal Pedagogy, Emeritus
Director of Opera-Theatre, 1987-1997
School of Performing Arts
Northern Arizona University
Flagstaff, AZ
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