Sound / by John Tyndall.

  • John Tyndall
Date:
1875
Catalogue details

Licence: Public Domain Mark

Credit: Sound / by John Tyndall. Source: Wellcome Collection.

    98/464 (page 60)
    it retreats it leaves a partial vacuum behind, the process being repeated by every subsequent advance and retreat. The whole function of the tuning-fork is to carve the air into these condensations and rarefactions, and they, as they are formed, propagate themselves in succession through the air. A condensation with its associated rarefaction constitutes, as already stated, a sonorous wave. In water the length of a wave is measured from crest to crest; while, in the case of sound, the wave-length is the distance between two successive condensations. The condensation of the sound-wave corresponds to the crest, while the rare- faction of the sound-wave corresponds to the sinus, or de- pression, of the water-wave. Let the dark spaces, <x, 6, c, d, fig. 25, represent the condensations, and the light ones, <x', 6', c\ d\ the rarefactions of the waves issuing from the * Pig. 25. A a a! b' c d d' fork a b : the wave-length would then be measured from a to 6, from b to c, or from c to d. § 6. Definition of Pitch: determination of Rates of Vibration. When two notes from two distinct sources are of the same pitch, their rates of vibration are the same. If, for example, a string yield the same note as a tuning-fork, it is because they vibrate with the same rapidity; and if a fork yield the same note as the pipe of an organ or the