The mechanism of the human voice

by Emil Behnke

Now these are the "Laryngeal sacculi" which, according to Mr. Illingworth, produce the falsetto voice by "acting in the same way as a hazel-nut can be made to act as a whistle, when the kernel has been extracted through a small hole in the shell," &c. I think, however, that the reader will, from the description given above, agree with me that the acoustic properties of the pockets of the voicebox cannot be very great, and that, at all events, there is a vast difference between their construction and that of a hazel-nut, either with or without the kernel. Then there is this additional difficulty, that even if one could whistle upon the pockets in the manner suggested, there are two of them, covered, let it be remembered, with a multitude of glands, continually producing moisture, and liable to enlarge or to diminish. How, I should like to know, could two such cavities be so tuned as under any circumstances to produce exactly the same tones? Would not rather frightful discords be the inevitable result? And again, what provision is there in the pockets for the gradations of pitch? But quite apart from these considerations, this and other similar theories are completely disproved by the fact that every tone which the human voice is capable of producing can be produced by inspiration as well as by expiration. The tones sung by inspiration are, as might be expected, wholly devoid of beauty, because the vocal apparatus is, as it were, put upside down, and the position of bellows and resonator reversed. But that does not alter the question. The fact remains, and clearly proves that the pockets have no more to do with the falsetto than with the chest voice, because in inspiration the air strikes the vocal ligaments after it has passed the pockets, and yet the result is, beauty of tone apart, exactly the same.

The function of the pockets, in my opinion, is this: They are the means of isolating the vocal ligaments, thus enabling them to vibrate freely and without hindrance. They also allow the sound-waves to expand sideways, thereby materially adding to their resonance. Lastly, they with their many little glands produce and supply the vocal ligaments with that moisture without which, according to the investigations of J. Müller,[H] the production of tone cannot be carried on.

Above the pocket ligaments there is a kind of tube which is formed by the upper part of the pyramids (surmounted by two little bodies called the cartilages of Santorini, [pl. XII], 7, 8) behind; the lid or epiglottis ([pl. XII], 9) in front, and sideways by two folds of mucous membrane running up from the pyramids to the lid ([pl. XII], 14, 10 and 15, 11). These folds are in many cases supported by two small cartilages, which we will call the Wedges ([pl. XII], 12, 13). These, according to Madame Emma Seiler, are the chief factors in the formation of the highest register of the female voice. In some physiological works they are treated as of very little consequence, and in others they are not mentioned at all.

These wedges are two thin strips of cartilage running in front of the pyramids ([pl. XII], 12 and 13) where they are embedded in a number of glands. Their upper ends terminate in the cartilages of Wrisberg (pl. XII, 14, 15), and their lower ends gradually dwindle away in the direction of the vocal ligaments.

Madame Seiler says that they "reach to the middle of the vocal chords, by which they are enveloped."[I] She comments in the same book on the fact that German anatomists have been reluctant to admit the existence of these cartilages; and she adds on page 61, "It was, therefore, a great satisfaction to me to find them described under the name of the cuneiform cartilages in Wilson's 'Human Anatomy.'" It must be confessed, however, that Wilson's description of them is totally different from Madame Seiler's. He says, "The cuneiform cartilages are two small cylinders of yellow fibro-cartilage, about seven lines in length and enlarged at each extremity. By the lower end or base the cartilage is attached to the middle of the external surface of the arytenoid (the pyramid), and by its upper extremity forms a prominence in the border of the aryteno-epiglottidean fold of membrane"[J] (i.e., the fold running up to the lid). According to Seiler, therefore, the wedges reach from the pyramids to the middle of the vocal ligaments, but according to Wilson their bases are attached to the middle of the outer surface of the pyramids, so that they cannot even touch the vocal ligaments. As Madame Seiler assigns very important functions to these wedges in the formation of the highest register of the female voice, and as she quotes Wilson in a manner that must lead the reader to suppose he gave a similar description to hers of these cartilages, I have thought it right to give Wilson's statement in full.

But there is a description of these cartilages by Dr. Witkowski which corresponds very closely with Madame Seiler's. Speaking of some of the glands of the voicebox, he says in the work mentioned before, on p. 12—"They are arranged in the form of an L, whose vertical branch goes along the arytenoid cartilages (the pyramids), the horizontal branch following the direction of the vocal cords. There is often found situated in the midst of this group of glands the cuneiform cartilage of Wrisberg, sometimes reduced to a mere cartilaginous granule."

Dr. Elsberg also describes them on p. 37 of the treatise before mentioned as "elongated nodules" in the hinder portion of the vocal ligaments, and says they are found "more often in the female than in the male sex." He calls them the "posterior vocal nodules," and gives on p. 36 a diagram which shows them most clearly and unmistakably. This point would therefore seem to be settled.

The Resonator.—We now come to the last part of our instrument, namely, the resonator, which is formed of (1) the pockets of the larynx; (2) the tube above the pocket ligaments; (3) the upper part of the throat; (4) the mouth; and (5) the nose. Before giving a description of the resonator, it will be necessary to make a few introductory remarks on certain laws of the philosophy of sound, which have been so clearly demonstrated that they admit of no contradiction.

Tone, as we have seen, is the result of rapid periodic vibrations.