2.3 Dynamic aspects of the singing voice
The strength of any sound (its intensity) is a subjective perception of sound pressure that depends on the amplitude of the vibrational motion of the sound source, that is, on the amplitude of vibration. The proportion of different levels of volume is called dynamics.
The oscillation amplitude of the sound source doesn't depend on frequency but it determines the strength of the sound. For example, if you first hit a piano string with a small hammer slightly, and then strongly, the pitch will not change. This will only change the amount of string vibration, i.e. the force with what the string will put pressure on the surrounding air particles. Thus, the greater the amplitude of oscillations of the air particles, the louder the sound will appear to be.
The voice power, as well as the height if its pitch, is produced in the larynx at the level of the vocal folds and increases with increasing force of the subglottic pressure. The power of the subglottic pressure reflexively affects the degree of vocal folds closure. The greater the power is, the tighter they are closed, trying to resist this pressure. The high is the pressure of the portion of air bursting through the glottis, the more energy it has, the greater is the degree of condensations and the subsequent thinning, in other words, the amplitude of the air particles vibrations increases and the pressure on the ear drum of our ear gets stronger. Thus, the subglottic pressure determines the power of the singing voice.
Each singer has his own limit of the sound amplifying due to an increase in the subglottic pressure. While singing crescendo at first there is a linear dependency between these values: the greater the pressure is, the louder is the sound. But very soon comes a point when, no matter how much the singer strains, his voice will not get louder, it will just turn into shouting, depriving the singing voice of his vocal qualities.
From the point of view of the vocal building physiology the subglottic pressure is controlled involuntarily by reflex movements of the diaphragm and changing volumes of the airways depending on the location of the articulation organs when pronouncing different phonemes. Limit value of the subglottic pressure depends on the overall physical and emotional condition of the singer's organism, on functioning of its endocrine and nervous systems, acoustics of the room and many other factors.
From the point of view of psychology the variations in it can be optional, depending on the intention of the singer to make a loud or quiet sound, of the sound energy that he intends to put into the singing in accordance with the performance objectives.
To characterize different musical dynamic gradations, including vocal sounds, the musicians made the following designations: f, mf, p, tr, and other shades of sound. Unlike pitch, they do not have a magnitude and are relative. Interpretation of their signification depends on the characteristics of our perception and processing of this information in our mind.
Specialities of the voice power perception by ear.
Our ear has varying sensitivity to the perception of sound intensity, depending on the pitch. Sounds that have the same power, but different height of pitch, seem to us to be different in volume. Our ear perceives high sounds as louder than low ones, although according to their absolute power of the sound pressure in fact they may be of same power. Thus, the power and the volume are not synonymous in terms of acoustics.
For a more accurate evaluation of voice power, or its magnitude, for research purposes it is usually measured with a special instrument, the audiometer. The unit of measure is decibel (dB).
Physiology of human acoustic sense is not equally sensitive to sounds of different heights of pitch. The scientists measured the threshold of acoustic sense throughout its range and determined its parameters.
The threshold of hearing is the level of volume that the human ear can barely distinguish.
The average threshold of human acoustic sense is calculated by measuring the threshold of acoustic sense of a large number of test persons with normal physical and musical sense. It can be represented as a diagram:
Illustration 11. The curve of average threshold of human acoustic sense.
As can be seen from the illustration, the threshold of human hearing for each pitch has a different sound power.
Each person's threshold of acoustic sense has its individual characteristics, but there is something in common: the human ear is most sensitive to frequencies between 1000 and 3000 Hz.
Thus, the voice power changes due to several factors: the tone pitch, the type of vowel, the method of articulation, physical (functioning of the endocrine system) and the emotional state of the singer, the sounding the resonators, vocal technique, etc.
Alignment of the vocal vowels.
Vocal teaching focuses on evenness of the voice on all vowels, as this is one of the main features of a good placed voice. That is why the alignment of vowels is one of the biggest challenges in working with voice. An experienced singer with a well-placed voice phonates all vowels in the same way, not only in power but also in tone. The "diversity" of the voice sounding, when all the vowels are formed in different ways, denounces an inexperienced singer.
For beginners, some vocal vowels sound better in terms of timbre and dynamics, other worse. This reflects their individuality. The teacher's challenge is to identify a transparent and good sounding vowel and to adjust all the other ones according to this model, avoiding a distortion of their phonetic character.
To "align" vowels means that the singer should try to preserve as far as possible a certain spontaneously formed on a well-sounding vowel articulation position during the singing of all the other vowels, that means to learn to sing all the vowels in one vocal position.
Singers distinguish a low and a high vocal position in terms of presence or absence of vibration in the singing mask.
From the acoustic point of view, the singing in a high vocal position is accompanied by a full resonance, and in the low one it is possible that the resonators don't participate at all. It influences the timbre of the vocal sound in a very distinctive way.
From the physiological point of view, the "vocal position" corresponds to the relative stabilization of the articulatory apparatus and the larynx position when singing different vowels, as a condition of aligning of their sound.
The task of aligning the vowels is associated not only with individual characteristics of a singer, but also with the vocal genre. Therefore, they can be aligned in different ways, depending on the voice sound due to stylistic traditions. For example, the academic singing traditionally implies a covered and rounded sound like in the vowels O, U. In Russian folk music the sound of the singing voice generated like the vowel E, and in the contemporary music the basic vowel is A. However, concert practice often reveals singers, sing folk and pop songs in an academic manner.
To align the vowels while singing at the same pitch the singer should strive to keep the soft palate in the same position for all phonemes, and while singing vowels of different pitches the rule should be: the higher the note is, the higher raises the palate. Only in this case a reflective rising of the larynx due to increased pitch can be avoided, and only like this you can maintain its relative stability while singing sounds different in pitch.
Depending on the placement of articulation reflex movements larynx can be observed as well as those of the diaphragm. This is how the coordination is reflected in the functioning of voice building complex that includes energy, generator and resonator system, in other words, the breathing, the functioning of the larynx and of the articulatory apparatus.
In singing with a placed voice the larynx and the diaphragm work like two ends of one barrel. Stabilizing of the larynx will contribute to the appropriate position of the diaphragm. That is why during phonational exhalation the students should try to maintain the basic inhalation position that corresponds with keeping the inhalational position, especially of the diaphragm, and thus of the larynx.
Correspondence between volume and pitch of voice.
Singing voice has a reflex correspondence of the voice power and pitch. With the rise of voice pitch the volume involuntarily increases, and vice versa.
This same feature of the voice serves as basis for many historically formed patterns of aesthetic regularities in the pronouncing of a musical phrase, in vocal as well as in instrumental music: the melody change upwards is usually accompanied by a crescendo, and the downward one by a diminuendo. The impression of the sound amplification in the melody movement upwards may be referred to the increase in the pitch.
Physiological feature of our hearing is that high-pitched sounds appear to the human ear to be more sensitive than the low ones. Therefore, if the singer sings an ascending scale with an equal voice power, the listener will feel that with the increase of the pitch the sound appears as if it is amplified. Due to the fact that the singer can optionally change the volume of the voice, he can also enhance this impression in a certain extent because of specific artistic challenges.
The ability to sing an ascending scale without amplifying the voice, i.e. to sing the high-pitched sounds without strain, as easily and safely as primary sounds in the speech range, is a sign of the correct vocal placement.