HANDBOOK OF ACOUSTICS - online book

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298
HAND-BOOK OF ACOUSTICS.
Royal University of Ireland, 1899.
1.    Explain the terms Pitch and Timbre, giving illustrations. See p. 29. For Timbre or Quality see p. 74.
2.    Find the vibration frequency of a note whose wave-length in air at 20° C is 2 ft. •
Ana.—Velocity of sound in air at 20° C is 1090 + 20 = 1110,
.,                .,_ „                        mo
therefore vib. frequency = —3— = 555
3.    How may the interference of sound-waves be illustrated by means of a tuning-fork ?
Am.—See pp. 141 and 142.
4     Describe the construction and use of a siren. Ans.—See pp. 31 and 32.
5     What difference exists, as a rule, in notes of the same pilch when sounded on closed and open pipes, respectively ?
Ant.—See p. 116.
6.    Describe an experiment illustrative of resonance.
Am.—Any of those described on pp. 59, 60, 62 or 63 will do.
7.    What difference is observable in the pitch of the note emitted by the whistle of a railway locomotive when it is approaching the listener as compared with that when it is going away from the listener ? Explain.
Am.—When the locomotive is approaching, the note is sharper than when going away. See No. 6, p. 285.
Royal University of Ireland, 1900.
1.    What are the ratios of the vibration-numbera of three notes which form a major common chord ? Show how from these ratios the frequencies of the notes forming a diatonic scale may be built up.
Am.—See p. 45.
2.  (a) Explain the necessity for a " tempered scale " ; (b) What ratio corresponds to the interval of a fifth on this scale ?
Am.—See first 8 pp., Chapter XVIII; (b) Equal temperament
presumed: V2 = 14982
3.    Define " overtone " and " harmonic." Name some instruments in which the overtones are harmonies, and others in which this is not the case.
Am.—For overtone, see p. 84.
Harmonic is evidently used here to denote overtones which are harmonic with the fundamental. For the former stringed instruments, organs, &c. For the latter anv of the instruments mentioned in Chapter XI.