2.4 Timbre of the singing voice
Tonal characteristics of the singing voice.
The timbre of the singing voice is the most important characteristics in the vocal art.
Often it is called vocal colouring or vocal colour. We can easily distinguish familiar voices due to their timbre. According to the timbre, vocal teachers determine the type of voice as well the degree of singer's professionalism.
The first concern of a vocal teacher is the freedom of the student's vocal tract while singing. Freedom or a strained sound can easily be distinguished by ear. Professionals appreciate resonance, roundness of vowels, smoothness of the transitions between registers, sonority and flight power voice, low or high vocal position, vibrato, wealth of timbre colours.
Describing the tonal quality of the voice sound by ear, musicians are not rare to give it a definition of visual, spatial, tactile character etc., for example, a pouring voice or a straight as a stick one. The sound of voices can be: round or flat, soft or hard, sharp, bitter or dull, matte, metallic or cotton, disintegrated or collected, chesty or heady, supported or with no support, weedy, active or sluggish, lowered in position or just low, white, open, or dark, covered, tremulous, nasal, pipe-like, velvety, hoarse, shrill, strangled, throaty, uterine, etc.
The variety of the singing voice sounding is the result of different combinations and changes in time of only three sound parameters: the vibration frequency of the sound source, the oscillation amplitude and overtone sound of the very singing voice.
These three characteristics our ear perceives as height, strength, and tone of voice.
Vowel formants in singing.
The primary sound is produced in the glottis. It turns out that is doesn't correspond with the sounds that we hear in the space. This sound has no timbre, no vowel or consonant form. In the formation of familiar speech sounds, recognizable by ear, the main role obviously belongs to the oropharyngeal channel. Due to a change in its form and emergence of resonance effects it is exactly in it that the final formation of the form of sound and timbre happens. Each vowel has its oral and pharyngeal formants. Their presence in the spectrum of vowels, pronounced by different people and at different pitch, allows our ear to perceive them in this form. These formants are called formants of vowels that are frequencies mainly determining these vowels. The remaining overtones that are present in the speaker's or the singer's timbre create his individual colour.
Let's cite some examples of the oral and the pharyngeal vowel formants:
- E - mouth cavity is small, vowel resonates at a high frequency of 3200Hz that approaches to the high singing formant and therefore is applied by vocal coaches for a high and light tone, and the pharyngeal formant is of 370Hz,
- U the throat is widely stretched, so it resonates at a low frequency of 900Hz and is recommended by teachers for finding chest resonance; the frequency of the oral formant is of 400Hz,
- O the pharyngeal formant frequency is of 1000Hz, the oral one is of 700Hz. The entire volume of the resonator becomes homogeneous, so singing teachers recommended that letter to be produced in a rounded sound,
- Ah is close to the vowel O and has the frequency of 700Hz and 1000Hz,
- Eh - 700 Hz and 1400 Hz.
The volume of the oral cavity increases in the sequence, E - Eh - Ah - O - U. The volume of the pharyngeal cavity is reduced in nearly the same sequence.
High and low vocal formants.
A classically trained voice can be referred as: bright, with lots of "metal" or "silver", rounded, soft, spacy, velvety. By analysing the spectrum of voice it has been found out that the "brilliance", "metal", "silver" are caused by the presence of so-called high voice singing formants, in other words, of the high-frequency region that concentrates 30-35% of the sound energy of the voice. For low voices, this high-frequency region is about 2,500 2800Hz, for high voices it is of about 3200Gts.
Vocal teachers have also the concept of the low singing formant in the area of 517Hz. The researches with the help of special equipment proved that this formant causes the thickness and the velvety character of the voice. A professional singer's voice is aligned due to the structure of registers and the ability to form the vowels in the way to preserve areas of high and low vocal formants. That's from the standpoint of acoustics can be explained by the phrase of Italian teachers: "Put the chest on the head, and the head on the chest."
The flight power of the voice.
The availability of high singing voice formants corresponds to the voice ability to go throughout the room, to fly over the orchestra. That is called the flight power of the voice. If we cut from the voice that high-frequency region, the voice will lose its lustre, become dull, distant, significantly reduced in strength. This high formant corresponds to the F4.
Radiographic studies of the singing process by professionals revealed that singers formed narrowing at the larynx entrance. The size of the cavity is 2.5-3centimeter, and therefore it resonates at a frequency of 2500-3000Hz.
High overtones appear in great quantities in the voice, if the singer uses a solid sound attack. If the attack is sluggish, the voice has an "disassembled" character.
Thus, the primary timbre on the vocal cords changes due to the resonance in the trachea, the larynx, the pharynx, and the mouth. Vocal formants appear in the pharynx and the trachea, throat and mouth form the vowel formants.
Acoustics also explains the presence of nasal sounds. If the soft palate is lowered, a channel is formed in the nasopharynx, absorbing frequencies of about 2000Hz. The absence of these frequencies in the voice the listener's ear perceives as nasal sounds.
The forward projection of the voice, directed at the viewer, depends on the presence of high singing formant. Acoustic shows that such sizzling sounds like S, TS, SH, CHTCH etc. have much higher frequencies in their range, so vocal coaches are extremely attentive to pronouncing of this type of consonants in terms of diction and a close sound.
The timbre of the singing sound is firstly determined by spectral composition, and secondly, it depends on the vibrato. By hearing a voice with a natural vibrato is perceived as free and warm. When vibrato frequency is of 6-7 cycles a second all the sound characteristics change: pitch, power, and timbre. If the frequency decreases, the effect of " rocking" appears. If the fluctuations occur more often, it is said that the voice has a "lamb" sound or a "tremolo". The voice changes in pitch of about ½ of tone when applying the vibrato, it vibrates around the middle frequency perceived as the main tone. The voice of the child mostly lacks vibrato. The singers distinguish the vibrato of the pitch, of the tone (at the same pitch the sound character changes from a lighter one to a darker one) and vibrato of the sound power.
High vocal position.
The high position of the sound is associated with the ability to customize the functioning of the body so that the voice has the area of high singing formant and that there is a concentration of energy of the singing voice in this area. This concept can be defined as a physiological adaptation of the vocal tract for the maximum voice power but not many efforts. That is why the vocal teachers work primarily on the high position of the sound, not on its power.