Sound / by John Tyndall.

  • Tyndall, John, 1820-1893.
Date:
1875
Catalogue details

Licence: Public Domain Mark

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

    47/464 (page 9)
    times repeated this experiment; first, in default of any- thing better, with a little tin cannon, the torn remnants of which are now before you, and afterwards with pistols. What struck me was the absence of that density and sharp- ness in the sound which characterise it at lower elevations. The pistol-shot resembled the explosion of a champagne bottle, but it was still loud. The withdrawal of half an atmosphere does not very materially affect our ringing bell, and air of the density found at the top of Mont Blanc is still capable of powerfully affecting the auditory nerve. That highly attenuated air is able to convey sound of great intensity is forcibly illustrated by the explosion of meteorites at elevations where the tenuity of the atmos- phere must be almost infinite. Here, however, the initial disturbance must be exceedingly great. The motion of sound, like all other motion, is enfeebled by its transference from a light body to a heavy one. When the receiver which has hitherto covered our bell is removed, you hear how much more loudly it rings in the open air. When the bell was covered the aerial vi- brations were first communicated to the heavy glass jar, and afterwards by the jar to the air outside; a great diminution of intensity being the consequence. The action of hydrogen gas upon the voice is an illustration of the same kind. The voice is formed by urging air from the lungs through an organ called the larynx, where it is thrown into vibration by the vocal chords which thus generate sound. But when the lungs are filled with hydrogen, the vocal chords on speaking produce a vibra- tory motion in the hydrogen, which then transfers the motion to the outer air. By this transference from a light gas to a heavy one the voice is so weakened as to become a mere squeak.1 1 It may be that the gas fails to throw the vocal chords into sufficiently strong vibration. The laryngoscope might decide this question.