HANDBOOK OF ACOUSTICS - online book

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

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16                      HAND-BOOK OF ACOUSTICS.
a second after the start; while in (b) the particle reaches the same points inand of a second, respectively. Now it is plain from the figure, that this difference in mode of particle vibration is accompanied by a difference in the form of the wave, and a little reflection will show that this must always be the case. "We have thus seen how the length, amplitude, and form of a wave are respectively connected with the time, extent, and mode of particle vibration.
Fig. 13.
Having now made some acquaintance with wave motion in general, we may pass on to consider the particular case of the sound wave. The first point to which we must turn our attention, is the nature of the medium. Air, like every other gas, is supposed to be made up of almost infinitely small particles. These particles cannot be very closely packed together; in fact, they must be at considerable distances apart in proportion to their size, for several hundred volumes of air can be compressed into one volume. When air is thus compressed, the particles of which it consists, press against one another, and against the sides of the containing vessel in all directions; and that with a force which is the greater, the closer the particles are pressed together; in other words, the air is elastic. An ordinary popgun will illustrate this : a certain volume of air having been confined between the cork and