22 HAND-BOOK OF ACOUSTICS.
A sound wave, like a water or rope wave, is determined by three elements, viz., its length, amplitude, and form. The length of a wave is the distance from any point in one wave to the corresponding point in the succeeding one; the amplitude is measured by the extent of vibration of its air particles; while the form is determined by the varying velocities of these particles as they perform their excursions.
The greater the amplitude (that is, the extent of particle vibration), the greater will be the degree of condensation and rarefaction.
In an associated sound wave, the direction of particle vibration is represented, for the sake of convenience, as being at right angles to its true direction.
The velocity of sound at the freezing point is 1,090 feet per second, and increases as the temperature rises.
The velocity of sound in water is 4,708 feet per second at 8° Centigrade.
The velocity of sound in elastic solids, such as iron and wood, is much greater than the above.