Introduction to the science of language, Volume 1 (of 2)

by A. H. Sayce

Apart from the respiratory organs which supply the fuel, the chief agents in the manufacture of speech are the throat and mouth. The breath, as it makes its way upward, passes the vocal chords, causing these to vibrate; and while the forms taken by the vibrations determine the quality or timbre of the sound to be uttered, the very essence of a vowel, for instance, consisting in the quality of the voice, the number of the vibrations determines its pitch.

In the pitch we have to distinguish between two things, the chest or true notes and the head or falsetto notes, respectively due to the position and action of the vocal chords. In the chest notes the vocal chords are stiffened and laid side by side, so that when the flow of breath comes from the lungs, they are forced aside for a moment, to spring back the next and cause a series of intermittent puffs of breath. In the falsetto notes, on the other hand, the muscles of the vocal chords are not contracted, nor is the glottis wholly closed; hence only the inner membrane of the chords is set in motion by the breath, and instead of actually meeting one another, the chords merely narrow or enlarge the aperture of the glottis.[149]

The forms assumed by the vibrations depend, of course, on the anatomical structure of the vocal chords, their greater or less elasticity, and the like. Besides quality and pitch, however, we must also take account of the intensity of the sound, this intensity or emphasis arising from the force with which the stream of breath is expelled from the lungs, and the corresponding strain of the muscles of the trachea and vocal chords.

In whispering, the amount of intensity is considerably diminished, though the pitch is quite as distinct as in loud voice. The glottis is not completely closed, but the upward flow of breath is not strong enough to do more than produce a sort of friction, or imperfect vibration in the vocal chords. The latter incline towards each other on the side furthest from the arytenoids, and so give the glottis a triangular shape; the larynx, however, may also assume other forms. Hence it is that we may distinguish three kinds of whispered voice. We may either have a soft whisper, where the whole glottis is narrowed, and the force with which the breath is emitted is very slight; or a medium whisper, where the force is greater, and only that part of the glottis left open which lies between the arytenoids; or a loud whisper, where the force is considerable, the false vocal chords are in close contact, and the epiglottis bent stiffly downwards, allowing but a very small opening for the escape of the breath. A loud whisper is rare; a medium whisper the most common. Sighing, it may be added, is produced above the larynx, which takes no part in its production; when the vocal chords are brought into action, the sigh becomes a groan.

It needs but a short experience to discover the numberless varieties of voice that may exist, and it is not uncommon for a blind man by this means not only to distinguish the age and sex of those he meets, but even to recognize his friends. In fact the human voice, from the deepest male to the highest female voice, has a range of nearly four octaves, the lowest note being E, produced by 80 vibrations per second, and the highest C, produced by 1,024 vibrations per second. But Vierordt has shown that in extreme cases its range is nearly 5½ octaves, from F (produced by 42 vibrations) to A (produced by 1,708 vibrations). In the same individual it is rare for the range of the voice to be more than two octaves, and in ordinary speech it is generally only half an octave. These different notes are due to changes in the length and tension of the vocal chords and their approximation or separation, the lower notes, for instance, requiring them to be longer, looser, and more widely separated than in the case of the higher notes, and consequently to admit a larger but less rapid current of air. It has been calculated that 240 different states of tension of the vocal chords must be accurately producible at will, in order to cause all the notes and intermediate tones heard in a perfect voice of ordinary range. Madame Mara could effect no fewer than 2,000 changes. The four chief varieties of the voice—the bass, the tenor, the contralto, and the soprano—are dependent on differences of pitch, that is ultimately on differences in the length of the vocal chords. The bass and the tenor with the intermediate baritone characterize the man, the contralto and soprano with the intermediate mezzo-soprano characterize the woman. The lowest note of the contralto is about an octave higher than the lowest note of the bass, the highest soprano about an octave higher than the highest tenor. Sometimes, however, we find a bass voice singing the higher notes of a tenor, and yet at the same time remaining bass. The reason of this is that the various kinds of voice differ not only in pitch, but also in timbre. This is caused by differences in the vocal organs. The larynx of women is smaller than that of men; the angle formed by it in front is less acute, and the cartilages are softer. The voice of boys is either contralto or soprano, like that of women, though generally different in tone. There is, however, no difference in the larynx of either boys or girls up to the age of puberty, when in the case of boys it rapidly increases in size, and the vocal chords become longer, thicker, and coarser.

The elevation or depression of the larynx exercises a certain modifying influence upon the voice. When the voice is raised from a low to a high pitch, the whole larynx, together with the trachea, is lifted towards the base of the skull. The exact way, however, in which the trachea and the parts above the glottis affect the voice is by no means clear. The thyro-arytenoid muscles, which extend from the arytenoids to the recessed angle of the thyroid cartilage, have much to do with the production of these higher tones. They narrow the diameter of the larynx just below the vocal chords, and the diminution of the calibre of the wind-tube nearest the chords thus occasioned heightens the pitch. On the other hand, the pitch is made to fall by semitones when the tube is lengthened. In short, the greater the strength of the current of air the higher is the pitch. The depression of the larynx produces the so-called veiled voice (vox clandestina), the larynx itself being then covered by the entire pharynx, the root of the tongue approximated to the palate, and the voice being thus made to resound in the upper part of the pharynx under the skull.

The precise nature of ventriloquism is not quite certain. J. Müller states that it may be produced by speaking through an extremely narrow glottis, during a very slow exspiration, performed only by the lateral walls of the chest, a deep inspiration having been first taken, so as to cause the protrusion of the abdominal viscera by the descent of the diaphragm. Magendie, however, considers it to be produced in the larynx by variously modifying the voice so as to imitate the changes otherwise effected in it by distance.

The character of the voice is necessarily modified by changes in the structure of the vocal organs, whether due to old age, to weather and climate, to exhaustion, or to disease. In old age the ossification of the cartilages, the diminution of muscular and nervous power, and the degeneration of the larynx, make the voice weak, tremulous, and “piping.” In damp chilly weather the voice is often lowered by as much as two or three notes: indeed, nothing affects it more rapidly than a damp and depressing atmosphere. Exhaustion, again, accounts for the dissonance sometimes perceived in the voice of singers, while inflammation of the lining membrane of the larynx, and other diseases, will impair or wholly destroy the power of utterance. Loss of voice during a bad cold is a familiar instance of the latter fact.