16. Notes on Acoustics⁶³

Acoustics has been defined as the science of auditory vibrations. It has also been defined as the qualities of a room or theater that determine how well a sound can be heard.w

What a singer knows about acoustics is generally limited to what he has learned through experience. Eventually he becomes aware that some places are easier to sing in than others. What he unconsciously listens for when he sings is a reflection of how his voice is sounding. This reflection is call­ed reverberation, which may be defined as a reflection of sound waves in a confined area.w The length of time that a sound can be heard in a closed area is called the reverberation time of that area. When applied to singing, if the reverberation time of a room is too short, that is, if the sound waves die out too quickly, then the singer's voice will sound lifeless and non-re son -ant to him and to the audience. If the reverberation time is too long, that is, if the sound waves keep sounding, then the singer's voice will sound too live, and interfere with the sounds coming after. An optimum reverberation time, which will vary with the size of a room or theater and the character of the walls and furnishings, will be the most satisfying to the performer and to the audience.64

There is usually no reverberation in outdoor singing where loud sounds are quickly dissipated. In cases like these, the singer wonders if his voice carries. In small rooms with hard surfaces there is usually too much re­verberation. Here the singer may well get the impression that he is better than he actually is. The most satisfactory situation is where the singer's voice fits the optimum reverberation time of the room or theater. Here the singer's vocal production will seem to be effortless.

In some instances it is possible to control poor acoustical conditions by sound reflectors and public address systems. Through the use of these aids a singer can learn to adjust his voice to fit the conditions, or depend on those operating the controls to do so.

The Vocal Mechanism65

The vocal mechanism may be said to be made up of bellows, vibrators, and resonators. The bellows-like action of the breathing mechanism fur­nishes the power in the form of a pressure flow of the breath to activate the vibrators, the vocal cords. Through the resistance of the vocal cords as vibrators to the pressure flow of the breath, acoustical energy is produced in the form of sound waves which are transmitted upward to the resonators -the pharynx, mouth, and nasal passages. Here the sound waves are changed into a singing quality, and a singing diction which should be considered as a part of the singing quality.

The singing quality is made up of musical tones which have pitch, loud-ness, and quality. The musical tones are basically sound waves which have, from a physical standpoint, frequency, amplitude, and timbre.

Frequency is the physical term for the number of vibrations of the sound waves, measured objectively. Pitch is the psychological term for the number of vibrations heard, and designated by letter names - c, d, e, etc. A sub­jective judgment.

Amplitude is the physical term for the size of the sound vibrations, measured objectively. Loudness is the psychological term for the strength of the tones heard.   A subjective judgment.

Timbre is the physical term describing the vibration form of the sound waves, in terms of the relative strength of the partials present. Quality is the psychological term for that characteristic of a tone which distinguishes it from another tone having the same pitch, loudness and duration.

The physical phenomena - frequency, amplitude, and vibration form -can be measured with reasonable accuracy with modern-day equipment. The psychological phenomena are difficult to measure accurately since they are sensations in the brain and vary in complex ways.

Pitch66

Pitch is the audible quality of a musical tone which reveals its position in the musical scale. In singing it is determined by the double vibrations per second of the vocal cords - the larger the number the higher the pitch, the smaller the number the lower the pitch.

Generally speaking, the vocal cords are more like wedges8,7and can vib­rate in three dimensions - depth, width, and length.   It is through their proper adjustments into at least three registers,    that the full pitch range and good intonation of the singing voice can be established.

The pattern of the register adjustments68- a low voice of an octave, a middle voice of a fifth, and a high voice of a fourth, with an additional third or more for the coloratura register, would seem to follow a natural law of vocal production in relation to pitch. Although the extent of the first register, beginning with the average pitch of the normal speaking voice, is quite de­finite , the extent of the second register is a variable depending on the vowel sound that is sung. The ah vowel sound fits the pattern of a fifth, since it is the last vowel sound that needs to change to the high register.

The register theory would seem to bear some relationship to the over­tone theory, at least within the overall range of the singing voice from low bass to coloratura soprano.

According to the overtone theory, all musical tones are complex. They are made up of a fundamental, which is the tone that has the lowest frequency, and tones above the fundamental which are called overtones. The fundamental is the first part of the complex tone and is called the first partial; the second part is called the second partial or the first overtone; the third is called the third partial and the second overtone, and so on. These partial tones make up what is called a harmonic series which follows a definite pattern above the fundamental, of an octave, a fifth, a fourth, a third, and on upward above the range of the human voice. The result is a complex combination of many partials which are difficult to pick out but are heard in the overall effect.

Loudness 69 Basically, loudness in singing is dependent upon the amplitude of the sound vibrations, which are dependent upon the pressure flow of the breath and the ability of the vocal cords to control this pressure flow. It is also dependent on the singing of open tone or open vowels, which cuts down on the amount of constriction in the mouth and throat, and which is conducive to an open or a large throat position. The result is a stronger action of the vocal cords and a free emission of tone.

Tone Quality 70

From a psychological standpoint, tone quality may be defined as that property of a musical tone that distinguishes it from another musical tone having the same pitch and loudness.w

From a physical standpoint, tone quality or timbre may be defined as the property of a musical tone which is determined by the number of partials present, and their relative strengths to each other .w" This is called vibra­tion form.

Differences in tone quality are due to differences in vibration form. The more complex the vibration form, the richer and more brilliant the tone quality becomes. Where there is a simple vibration form, for example, where the fundamental is sounded alone, the result is a pure tone, which is dull in quality. This can be illustrated by singing a falsetto oo which is es­sentially a pure tone.   The vibration form of the falsetto is a regular and

symmetrical curve which is called a sine curve. The addition of one or more partials changes a simple vibration to a complex vibration form.7'

The Formant Theory of Tone Quality72

According to the formant theory, the characteristic quality of a musical tone is due to the relative strengthening of whatever partials lie within a fixed region of the sound spectrum. With a change in the pitch of the funda­mental, so that another partial comes in the formant range, this partial will be strengthened, and the vibration form will change. This is in contrast to the harmonic theory of tone quality, where the vibration form does not change with a change in the pitch of the fundamental,

An application of the formant theory was used first as an explanation of vowel differences. An analysis of vowel sounds shows that each sound is characterized by two major frequencies.73

The Singer's Formant74

According to Bartholomew, good tone quality in singing is dependent upon a low formant centering around 600 cycles, and on a high formant centering around 2800 for men, and a trifle higher for women. Both of these formants, according to Bartholomew, are dependent upon the large or big throat. The lowformantis the basis for resonance, or roundness, or sonority, and is the result of a strong pharyngeal resonance. The high formant is the basis for ring of brilliance in the voice, and is thought to be the result of resonance in the laryngeal chamber.75

According to analyses of singing by Rshevkin,    there are doubtless in good, well trained voices characteristic singing formants which are prac­tically the same for all vowels. Characteristic vowel formants appear only at the beginning of the vowel after which there is a change to the singing formant. According to Rshevkin, these investigations are in agreement with the investigations of Bartholomew, as to the part the high formants play in the production of a good singing tone.

There are many possible variations in tone quality in the singing voice. However, it is not a question of how many tone qualities a singer can sing, but rather which one he should sing to get the best results from his vocal mechanism. This means that a basic quality should be established first, in an even scale of normal resonance, in terms of the singer's identity. Or in other words, a singing tormant should be established first.

Are You Ready To Move Onto The Next Lesson? Click Here...