Elementary Lessons on Sound

Elementary Lessons on Sound

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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1879 edition. Excerpt: ...lowest tone of which is reinforced by a resonance cavity, and thus communicated to the air. To set them in motion they are placed between the poles of an electro-magnet, the current in which is regulated by a separate apparatus. To make their sound audible, the resonance chamber has to be brought near them. Its mouth can be closed by a lid attached to a lever, by partial opening of which, the sound can be regulated to any amount of strength. The strings acting on a number of such levers are attached to a sort of key-board. Helmholtz at first experimented with eight forks of this kind, representing B, and its first seven harmonic partials, namely b, f. V d," f" a," and V'i, . He afterwards had forks made of the pitch of d'," f" a'" and V'% To set them in motion, intermittent currents had to be passed through them equal in number to the vibrations of the lowest in a second, namely 120. The fundamental fork thus received an impulse at every vibration, the higher members of the series at periods inversely corresponding to their rapidity. The moving apparatus consisted of a tuning-fork, to the two prongs of which were fixed platinum w.ires. dipping in cups filled half with mercury and half with alcohol. These made contacts at every oscillation, which, sending an intermittent current through the electro-magnet, secured persistence of the vibration. A little steel clamp was placed on one prong of the fork, by which its oscillations might be brought into exact unison with the fundamental tone. When the resonance chambers were closed, and the whole series of forks was in vibration, nothing was heard but a gentle humming sound, but on opening each of these, its corresponding tone was heard, and it became possible to form...show more

Product details

  • Paperback | 70 pages
  • 189 x 246 x 4mm | 141g
  • Rarebooksclub.com
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 123653784X
  • 9781236537843