Popular Science Monthly/Volume 64/January 1904/Voice, Song and Speech
|VOICE, SONG AND SPEECH.|
By WM. SCHEPPEGRELL, A.M., M.D.,
NEW ORLEANS, LA.
THERE is no physical faculty which so distinguishes man from the lower animals, and marks him more conspicuously in the image of his Maker than the power of articulate speech. That there is some means of communication among the lower animals, we can not doubt, but that faculty of articulate speech which enables us to communicate to our fellowmen not only our ordinary desires and wishes, but even the most delicate shades of our inmost thought, that faculty belongs distinctively to the human race.
This subject may be treated from various standpoints, but we will here limit ourselves to a strictly physical consideration, explaining first the general anatomy of the parts essential in the production of the voice, and afterwards the manner in which these are used in the formation of song and speech.
Before discussing the subject of the voice, we must have some conception of sound in order to understand more fully how the voice is produced and how it is modified by the various parts concerned in the faculty of speech. All sounds are due to the vibration of the surrounding air, which conveys to the ear the vibrations produced by the sound-producing object. Perhaps one of the simplest methods of producing sound is by means of the tuning fork. When this is struck the prongs are made to vibrate, and these in turn set up in the air vibrations which are carried to the drum of the ear, and thence transmitted to the brain as sound.
In sound we have three important qualities, pitch, loudness and timbre. The pitch depends upon the number of vibrations which the sounding body makes in a given time. When these vibrations are repeated less than eighteen times per second they produce no musical tone to the ear. When a boy strikes a stick against a paling fence we have simply a rattle. If, however, this could be done so rapidly as to make more than eighteen beats to the second, then the ear would cease to recognize each individual stroke and would perceive a musical tone. The more rapid the vibrations the higher the tone, until the limit of human hearing is reached, which is about 48,000 vibrations to the second.
The second quality of sound, which we may call 'loudness,' is due to the range of the vibrations made by the sound-producing body. If the tuning fork is struck lightly, it gives a certain tone, but very softly. If it be struck hard, however, it produces a louder sound, due to the fact that the vibrations are greater in length, which, being communicated to the ear, set up stronger vibrations in the drum, and we hear a louder sound. This, however, does not vary the pitch of the sound which remains identical as long as the number of vibrations per second remain the same.
The third quality of sound is due to the form of the vibrations regardless of the pitch or the loudness. The trained ear recognizes, for instance, in the note of the tuning fork, the violin, the clarionet and the piano, the same tone howsoever made. There may be the same degree of loudness, but there is a distinction—this distinction being due to the peculiar form of the wave set up in the air and thus communicated to our ear. This is known as the timbre of the sound.
The manner in which the ear distinguishes the loudness and the pitch is easily understood, as the vibrations of the drum of the ear correspond in degree and number to the vibrations of the air and of the sound-producing body. How it distinguishes the timbre of the sound is much more complex. This subject has been carefully investigated, and it is now accepted that with the original or fundamental tone there are always a certain number of over-tones which give this special quality to the sound.
Having now explained some of the fundamental principles of sound, we will discuss the question of how the human vocal apparatus produces that form of sound known as the voice. Undoubtedly the human voice is based upon the same principles as other musical sounds, being, however, more complete, more varied in its capacity and more adjustable to surrounding conditions, than any instrument made by human hands.
The relationship of speech to song is not well understood, many persons believing that in song some special parts of the vocal organs are utilized which are not employed in ordinary speech. As a matter of fact, however, speech is simply a modified form of singing, the principal difference being in the fact that in singing the vowel sounds are prolonged, and the intervals are short, whereas in speech, the words are uttered in what may be called 'staccato' tones, the vowels not being specially prolonged and the intervals between the words being more distinct. The fact that in singing we have a larger range of tones does not properly distinguish it from ordinary speech. In speech we have likewise a variation of tones, and even in ordinary conversation, there is a difference of from three to six semitones, as I have found in my investigations, and in some persons this range is as high as one octave. In this consideration of the voice, therefore, song and speech may be considered under one head.
In the voice, as in other forms of sound, we must have, first, a vibrating body to initiate the sound. This we have in the vocal cords of the human body. The vibrations set up in the vocal cords (Fig. 1) are not due to a violent impact, as in the case of the tuning fork, as this would injure the delicate tissues of the sound-producing organs, but are caused by the air passing between the vocal cords very much as the current of air sets up vibration in a reed instrument such as the clarionet. In the human voice this current of air is furnished by the lungs, which have therefore the double duty of supplying the oxygen to the blood and setting up vibrations in the vocal cords for the voice.
The chest is supplied with the most perfect mechanism for obtaining this current of air. The main support is furnished by the ribs, which give firmness to the chest. These are held together and supported by muscles of great strength which raise the ribs in the act of inspiration. The lower part of the chest is enclosed by a broad flat muscle known as the 'diaphragm,' which materially assists in giving its bellows-like faculty to the chest. In the act of inspiration, the diaphragm is lowered and the ribs are raised, thus creating a space in the lungs which is filled by the air entering through the nose and throat. In expiration, however, this is reversed, the ribs being lowered and the diaphragm raised, the process being assisted by the natural elasticity of the lung tissue. The thorough understanding of this function of the lungs should impress us with the importance of not hampering their action by tight clothing or lacing, which necessarily interferes with their freedom of action, and, by thus lowering the resistance of the body, make it more liable to the entrance of disease.
The two vocal cords, whose vibration forms the essential factor in the voice, are situated within the larynx, the most prominent point of which is known as the 'Adam's apple.' The larynx has several plates of cartilage which, while protecting the delicate organs within, make it less liable to fracture or injury than if they were made of bone. By removing one of the plates of the larynx, we see the edge of one of the vocal cords, which consists of a narrow band of rather hard tissue, whitish in color in health, and surmounted on a band of muscles which not only gives it support but also enables it to adjust the tension necessary for tone-formation. The vocal cords, during the act of inspiration (Fig. 3), are wide open so as to allow the free ingress of air, and even during ordinary expiration (Fig. 3) they remain sufficiently wide open not to hamper the freedom of respiration. When the voice is used, however, the lungs having obtained the necessary supply of air, the edges of the vocal cords are brought together (Fig. 1), and, as the air is forced through them by the contraction of the lungs, they are set up in vibration, thus producing the voice.
Two vertical sections of the larynx are shown in Figs. 4 and 5 (after Merkel), the former showing the vocal cords (1, 2) in the lower register, and the latter the vocal cords (1, 2) in the high register. In both Figs., 5 and 6 represent the pockets or ventricles of the larynx, and 3 and 4, the ventricular bands, sometimes called the false vocal cords. Figs. 7 and 8 show a section of a cartilage of the larynx.
The voice, like other sounds, varies in pitch, loudness and timbre. The pitch is due to the tension of the vocal cords, the process, however, being somewhat more complicated than in a violin in which there are several strings. There being but one pair of vocal cords in the larynx, the tones are produced, first, by tightening the vocal cords, and, when the limit has been reached, so that a greater degree of tension would be injurious to the vocal cords and the muscles which control them, there is set up a different form of vibration known as the change of register. This subject of the register is somewhat complicated,
but it will be better understood if we suppose that the difference between a low and a high register is due to the fact that in the latter a shorter portion of the vocal cords is set into vibration.
The bass, for instance, produces his lower tones by increasing the tension of the vocal cords until B flat (International Pitch) is reached when he changes his register, obtaining his remaining upper tones by contracting the vocal cords in this register. The untrained singer, however, not understanding this change of register, may attempt to reach the upper tones by simply increasing the tension in the lower register, this soon resulting in hoarseness, inflammation and perhaps permanent injury of the voice.
The ordinary method of speaking of these registers as the 'chest,' 'throat' and 'head' registers is apt to be misleading, as in every case the tones are formed in the larynx and by the vocal cords, the 'head' and other names being derived from the fact that the sound seems to be more directed to these parts of the body.
The loudness of the tone is due to the force with which the air is expelled from the lungs, thus causing a greater range of vibration in the vocal cords. The question of timbre is much more complex. It is this feature which distinguishes the singing of the amateur in music from the professional, the uncultivated from the cultivated voice, and the resonant tones of the orator from the poor voice of the ordinary speaker. As already explained, the quality of tone is entirely influenced by the number of over-tones, these being due to other parts of the throat accessory to the vocal cords in voice production.
Before explaining this point, we must first consider what other organs are essential in the production of the voice. The fundamental tones are made in the larynx as already explained, but these alone do not produce articulate speech; in fact, such tones are not limited to the human race. It is the peculiar faculty of articulating that distinguishes the voice of man from that of other animals. Articulation is due to other parts concerned in the organ of speech, such as the tongue, the teeth, the lips, the palate and the nostrils. Each of these has its influence in the formation of the voice, and a defect in any of these will be easily recognized by the experienced hearer.
The fundamental element of the voice is formed by the vowel sounds, the consonants, as the name indicates, simply modifying the vowel sounds. Although nominally the pure vowels are a, e, i, o and u, the vowel sounds are of far greater number. For instance, the a occurs in 'maw,' 'hat' and 'mate,' but in each it is sounded differently and the same occurs with the other vowels.
The simplest vowel is a (as in 'ah') which is sounded by vibrating the vocal cords, the sound issuing almost without obstruction, the tongue being lowered and the lips apart. If now, without any further change than to round the lips, the same effort be made, the a will be changed to o, and if the lips are still further contracted the o will be changed to u. The remaining vowels a (as in 'hate'), e and i are made from the fundamental a above described, by contracting and shortening the passage between the tongue and the roof of the mouth and palate. If we would suppose that the passage from the vocal cords to the lips were a tube, then we could say that in u the passage was the longest and in i the shortest, and the o, a and e sounds intermediate between these in the order stated. In these and in the examples which follow, it would be well for the reader to test the methods described, which would do much to make this subject more easily understood.
The consonants, as their name implies, can not be sounded alone but simply modify the vowel sounds. This may be done by the lips (labial), the teeth (dental), the tongue (lingual), the palate (palatal) or by allowing the air to pass through the nostrils (nasal). The simplest are the labial sounds (m, b, p, f, v, w), and these are therefore, the first learned in infancy, as 'mama,' 'papa,' etc. In sounding the vowel a, we first contract the lips and then allow the air to escape by opening them, the slight explosive sound forms 'ba,' and if this effort is made stronger, it becomes 'pa.' In the dental sounds (t, d, s, etc.), the emission of the vowel is made by the teeth and tip of the tongue, and in the palatal (k, g, c, etc.), by means of the middle or posterior portion of the tongue and the middle or posterior portion of the palate. In this position are formed the so-called 'guttural' sounds of the German (ich, doch, etc.) which forms one of the characteristics of this language.
In the above described consonant sounds, the emission of air through the nostrils has been prevented by the soft palate being brought against the back of the throat. In the nasal sounds (n, ng), however, the air is allowed to pass through the nostrils by relaxing the soft palate. If the nostril be closed when 'ing,' for instance, is to be pronounced, the sound will not issue unless the air be allowed to pass through the nostrils. In some cases, the nasal sound is given to words to which it does not belong, this giving a peculiar nasality of tone easily recognized. In the French, there are normally the 'nasal vowels' (in, en, on) characteristic of this language.
In addition to the above, we have the aspirate, represented by the letter h. In this, a partial expiration is first allowed to pass between the vocal cords before they are approximated to form the vowel, in this way changing the a to 'ha' and o to 'ho.' This sound is pronounced very distinctly in the German language, less so in the English, being occasionally omitted as in the words 'heir,' 'humor,' etc., and infrequent in the French and quite softly when pronounced.
The aspirate, which is sounded without approximating the vocal cords, brings us to the whisper in which we have all the elements of speech without the initial vibrations of the vocal cords. That these are not concerned in the whisper is demonstrated by the fact that persons, suffering from such forms of paralysis that the cords can not be brought together, can whisper, and that even where the vocal cords have been entirely destroyed by tuberculous or other disease, the patient can still whisper without difficulty.
As already stated, the modifications of the vowel sounds for articulate speech are made in the cavities of the mouth, the upper part of the throat and by the nostrils, and are further modified by the position of the teeth, lips and palate. In perfect singing or speaking, we must have all these parts in a normal condition, and where there is no obstruction, defect, congestion or inflammation, there is no interference with the free motion or vibration of the parts concerned in voice production.
The question may be asked how this information about the action of the vocal cords has been learned, since, during life, they are out of sight. The use of a mirror by the throat specialist is now so common that it no longer attracts any comment, although this method of examining the larynx of a living subject is yet comparatively recent. The method, however, by means of which these parts are inspected is not so well understood, and it would, therefore, be not without interest to explain it.
The interior of the larynx, being separated from without by its skin and cartilages, is, of course, dark, and must therefore first be illuminated in order to be seen. A small mirror is therefore placed in the back part of the throat, which projects the rays of light downwards into the parts to be inspected. In order to enable the operator to use the same mirror for inspecting as for illuminating the larynx, he fastens to his forehead a concave mirror which reflects the condensed light to the throat mirror, and by means of an opening in the center of the head mirror, he is enabled to see the parts of the throat that are illuminated by the throat mirror. This arrangement, which is comparatively simple, has been the foundation of the science of laryngology, as, before its invention, the investigations of the larynx were limited to the examination of the dead body, and many of the most important diseases escaped observation.
The study of the action of the vocal cords during speaking or singing is somewhat more complicated. We have already stated that in order to produce a tone, the rate of vibration must be at least 18 to the second, and the lowest tone of the human voice (low D of the bass) rarely falls below 73 vibrations per second. Ordinarily, then, it would be impossible to see the motion of the vocal cords during vibration, and yet this is an important matter. Human ingenuity has come to the relief of this problem in the invention of an instrument called the 'stroboscope' which is here shown.
In explaining its mechanism let us imagine a carriage wheel with a number on each spoke, the wheel being in rapid revolution around its axis. Ordinarily these numbers would be entirely obscured on account of the rapidity of the motion, and would present to the eye simply a blur. If, however, we place in front of this wheel a large piece of pasteboard with an opening opposite to one of these numbers, and some mechanism in front of this hole so that it would open only when the same number is in front of it, then we could inspect them one by one by a simple adjustment. Furthermore, it could be so arranged that instead of opening always at the same number, it would miss one revolution and open at the second number, and in this way we could see each number until the whole series had passed.
This is the principle involved in the stroboscope. The patient is instructed to give a certain tone, and by means of a syren, which indicates the number of vibrations for any given tone, the number of vibrations per second are registered. This instrument is then so adjusted that the aperture, by means of which the vocal cords are examined, opens after every series of vibrations are complete so that the vocal cords are always in the same position. This inspection of the larynx is conducted in the same manner as with the mirror method already described.
In this way the vocal cords may be seen in any stage of their vibrations, and the instrument may also be so adjusted that one series of vibrations is omitted, and the second step of the vibration is taken up, so that we apparently have a slow motion of the vocal cords, which enables us to study their action during voice production. This has given us much useful information, especially regarding the subject of the various registers of the human voice.
Having now explained the production of the voice under normal conditions, I must now show how this is affected by abnormal conditions, and also point out some suggestions as to the care of this important organ. You will remember that the vibrations of the vocal cords produce the fundamental elements of the voice. Any condition which prevents their free vibration will therefore interfere with the normal voice. The most frequent disturbances are due to 'colds' in which the vocal cords may become congested or inflamed. This produces a thickening of the vocal cords which lowers their rate of vibration, and, consequently, lowers the tone and gives rise to the hoarse voice characteristic of an ordinary cold. When this condition, from any cause, becomes chronic so that instead of a simple swelling of the vocal cords we have a chronic thickening, it may leave, unless corrected, a permanent defect in the voice.
A more serious influence on the voice is due to growths or tumors either on the vocal cords or in some other part of the throat, and interfering with the formation of vocal sounds. In the adjoining illustration, the small tumor shown between the vocal cords had caused hoarseness by interfering with the vibrations of the vocal cords, and by irritating the throat had set up a persistent cough. About eighteen months before being seen, the patient had leaped into the Mississippi River to save a child from drowning. The exposure was followed by a severe cold, leaving a persistent hoarseness, afterwards accompanied by a cough. About a year and a half afterwards, the patient was sent to me and a careful examination revealed this small tumor on the vocal cord, which affected his speech, so that it was of an extremely husky character. The following day this tumor was removed by means of an instrument passed from the mouth into the throat, the course of the operation being followed by means of a mirror as already explained, and being rendered painless by the application of cocaine, and the tumor removed. The voice being freed from the dampening influence of the growth, was restored immediately, and the cough disappeared a few days later,
A still more serious injury to the vocal cords is due to ulceration which has destroyed some part of the vocal cord. A defect of this kind is irreparable. When an arm is diseased, no matter how seriously, there is always a possibility of saving it, but when the arm is cut off, its usefulness is ended. This is also the case with the vocal cords. By means of training, the voice may to some extent be improved, but it will always be more or less affected when there has been a loss of substance.
Paralytic conditions also have a marked effect on the voice. As already explained, in the production of sound the edges of the vocal cords are brought together. In cases of paralysis, if one or both vocal cords can not be brought to the middle line, the space is too large to resist the column of air from the lungs for setting the vocal cords in vibration, and there is no voice. In some cases, where the paralysis is on one side and not too great, the remaining vocal cord may be gradually trained to be brought over to the other side, and in this case the voice may be recovered, otherwise it will be simply a whisper. Some cases of paralysis involve only the muscles which contract the vocal cords, thus preventing tension and causing hoarseness. As there is no loss of substance in paralysis, the prospects for recovery of the voice, except in certain cases, is good.
As we have already explained, the principal parts concerned in the modification of speech are the lips, teeth, tongue, palate and nostrils, and any defect in these will influence voice production. Some defects are easily recognized, as for instance the tie-tongue, in which the band, which connects the tip of the tongue with the floor of the mouth, is too short and prevents the tongue from being brought forward in certain sounds, thus giving rise to the defect characteristic of this condition. This defect is easily rectified by a slight operation, and, unless the muscles of the tongue are otherwise defective, restoration of normal speech eventually ensues.
It must be remembered, however, that in children who have for years been accustomed to this defective method of speech, the muscles have adapted themselves to the changed condition, and a complete correction of the defective speech is a question of time. I remember an occasion, for instance, when a mother returned to me after this simple operation had been done, and complained that it had been a total failure, giving as her reason that the child's speech was just as defective as before the operation. I explained to her what I have just said, and instructed her to teach the child to use its tongue in its normal position, and this exercise was followed in a few months by an entire correction of the defect.
Missing or broken teeth, especially in the case of the front teeth which are more concerned in voice production, give rise to defects which are corrected when the teeth are replaced or repaired.
A catarrhal condition in the upper part of the throat, filling it with secretion, interferes with the free vibration of sound and gives an effect very similar to that due to an obstruction in the rear portion of the nostrils, as is sometimes the ease in the later stage of a severe cold.
There seems to be much misconception regarding the tonsils as a factor in voice production. It is of common occurrence for mothers to ask the physician before an operation upon the tonsil if it will not injure the voice. As a matter of fact, the healthy tonsil has no effect upon the voice, while the diseased tonsil can have only an injurious effect either directly by its size, interfering with the free vibration of the voice, or indirectly by setting up an irritation of the throat and causing the voice to be weak. The correction, or even removal, of a diseased tonsil can, therefore, have only a good influence on the voice.
There is another unhealthy condition of the throat of children which is now receiving more attention, due to the so-called 'adenoids.' In this there is an enlargement of the tissues in that part of the throat just back of the nostrils. This growth may interfere with speech either on account of the secretion which it produces or by its size, in either case obstructing the entrance of the nasal sounds into the nostril. The presence of this abnormal growth is injurious not only on account of its effect on the voice but also on the general health, as it prevents the child from breathing in the manner intended by nature, that is through the nostrils.
The nostrils are not simply openings for allowing the air to reach the lungs, but their special function is to warm, clean and moisten the air which is intended for respiration. Proof of this is shown by the fact that if we suffer from a 'cold' so that the nostrils are obstructed, an irritated throat is a certain result the next morning, being due to the fact that the unprepared air has irritated the delicate tissues of the throat. In diphtheria, for instance, if the membrane has developed in the throat and threatens the breathing of the child, and this be overcome by a tube inserted in the throat below the false membrane, respiration must now go on without the air passing through the nasal passages. The only way to counteract the evil effects of this abnormal breathing is to place the child in a room which is warmed to almost the normal temperature of the body, artificially saturated with moisture, and every endeavor made to keep it free from impurities. Even with this, the patient may develop a bronchial affection due to the absence of nasal breathing, but without it, a bronchitis, even of a fatal character, would develop in a short time. I go to some length in explaining this matter, as the importance of the nose in respiration is not well understood. Its influence on the speech is better recognized, as most persons easily note the peculiar effect on the speech when there is an obstruction in the nasal passages.
Having now given you a description of the organs of speech in health and in disease, a few words as to its care will conclude this article. In this as in other parts of the human body, prevention is better than cure. Careful attention to any abnormal condition of the nose or throat is an effective means of preventing any disease of these parts. The same rule, which applies to other parts of the body, such as the necessity of outdoor exercise, fresh air, etc., is in general applicable here, and perhaps a little more here because the nose and throat form the vanguard of the respiration so essential to life. Any agent which irritates the delicate membrane of the throat is injurious to the voice—among these may be mentioned the use of strong liquor and the abuse of smoking, especially cigarettes. The action of the cigarette tends to produce a chronic irritation and thickening of the throat, sometimes accompanied by excessive dryness and irritability, these causing efforts to clear the throat which adds to the injurious effect. The remedy is evident.
The correct placing of the voice is of the utmost importance. No attempt should be made to do this until the voice is properly developed, and this should not be done by singing or even solfeggio practice, but by vocal exercises on the vowel sounds, especially of a (as in 'maw'). I have seen many voices greatly injured and even permanently ruined by being placed in the wrong class, even such egregious errors as a bass, classified as a tenor, being among the cases which I have had to treat.
The strengthening of the throat by means of vocal exercise is as important as the strengthening of the body by suitable physical exercise. Teachers and lawyers, therefore, as well as singers should practise certain vocal exercises such as loud reading, light vocal scales, etc., so that, when called upon to make a special use of the voice, it is prepared by regular practise for this unusual exertion.