HANDBOOK OF ACOUSTICS - online book

A complete view of Acoustical Science & its bearings on music, for musicians & music students.

Home | Just The Tune | Order | Contact




62
CHAPTER VI.
—♦—
On the Intensity or Loudness of Musical Sounds.
We have seen that the pitch of a sound depends solely upon the rapidity with which the vibrations succeed one another. We have next to study the question: "Upon what does the Loudness or Intensity of a sound depend P "
Gently pluck a violin string. Notice the intensity of the result­ing sound, and also observe the extent or amplitude of the string's vibration. Pluck it harder; a louder sound is heard, and the string is seen to vibrate through a greater space. Pluck it harder still; a yet louder sound is produced, and the amplitude of the vibrations is still greater. We may conclude, from this experiment, that as long as we keep to the same sounding body, the intensity of the sound it produces, depends upon the amplitude of its vibrations; the greater the amplitude, the louder the sound. This fact may be strikingly illustrated by the following experiment. Fasten a style of paper, or better still, parchment, to one prong of a large tuning-fork. Coat a slip of glass on one side with lamp­black, and lay it, with the coated side upwards, on a smooth board,
Fig. 29.
having previously nailed on the latter a straight strip of wood, to serve as a guide in subsequently moving the glass slip. Now strike the fork sharply, and immediately hold it parallel to the glass, in such away, that the vibrating style just touches the lamp-