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.
