Voice production in singing and speaking, based on scientific principles

by Wesley Mills

CHAPTER VII.

SOUND—THE LARYNGOSCOPE—THE LARYNX RECONSIDERED.

Before discussing our subject further it is desirable that some attention be given to a few of the fundamental principles of that department of physics termed acoustics, and which deals with the subject of sound. If the student has the opportunity to study this subject theoretically and practically, as it is set forth in some good work on physics, he will have no reason to regret the time spent. A deep knowledge of the laws of sound is not absolutely essential, or even highly necessary, for a sufficient understanding of the principles involved in voice-production. It is, however, all-important that a few facts and principles be thoroughly grasped.

For those who feel that they have the time for a study of acoustics, the author would especially recommend Tyndall's work on sound, in which the subject is treated with wonderful clearness and charm. What we endeavor now to bring before the reader we have found sufficient for nearly all the purposes of the voice-user.

An observer on the street, looking at a military band, notices certain movements of one member of the organization which result in what he termed the sound of the drum; but a deaf man by his side, though he sees the movements, hears nothing. This, being analyzed, means that the movements of the drummer's arm, conveyed through the drumstick to the membrane of the drum, give rise to movements in it which set up corresponding movements of the air within the drum, which again cause movements of the body of the instrument, the whole causing movements of the external air; and here the purely physical process ends. The movements other than muscular ones are not readily observed, but experiments not only prove that they exist, but demonstrate their nature, even to their exact rate of occurrence, their size, etc. These movements are termed vibrations, and, as has been indicated previously, they are the sole physical cause of sound. But that the latter is not due wholly to a physical origin is evident from the fact that sound for the deaf does not exist. It must, therefore, be a personal, a subjective experience, and as the sleeping, unconscious person does not necessarily hear a sound, the process is not wholly a corporeal or physiological process; it is finally an experience of the mind, the consciousness, and so is psychological as well as physiological.

The fact that sound has a physical basis in the vibrations of bodies, either solid, liquid, or gaseous, may be brought home to one in various ways. Concussion or shaking of some kind is essential to start these vibrations. The air is made up of its particles, and one being moved sets up, inevitably, movements in neighboring particles on all sides, hence vibrations travel in all directions; which explains why a sound in the street may be heard by those in every part of the street not too distant, and also in the upper rooms of the houses and below in the basements. This is an important fact for the singer or speaker to bear in mind. His purpose must be to set up vibrations that will travel with great perfection and rapidity in all directions.

The following experiments of a simple kind will serve to convince those who may not have given much attention to the subject that sound is due to movements of some object, which we term the sounding body, strictly that which starts the vibrations by its own movements or vibrations.

If a sufficiently flexible band of metal or a stiff piece of whalebone be fixed at one end in a vice, and then sharply pulled to one side and suddenly let go, a sound results. The same effect is produced when a tight cord or small rope is plucked at and then suddenly released. In each of these cases, if actual movements are not seen, a certain haze which seems to surround the object may be observed. The same can be seen when a tuning-fork is set into action by a bow, a blow, etc. In the case of the fork a graphic tracing ([Fig. 36]) can be readily taken on smoked paper, thus demonstrating to the eye that vibrations exist, that they occur with perfect regularity and with a frequency that can be measured.

Fig. 36 (Tyndall). Illustrates how the vibrations of a tuning-fork are registered on a blackened (smoked) glass. In order that the movements of the fork shall be traced in the form of regular curves, the surface must be kept moving at a definite regular rate.