HANDBOOK OF ACOUSTICS - online book

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EXAMINATION PAPERS.                         277
(J) How would you demonstrate their existence (1) in vibrating strings, (2) in organ pipes ?
Am. (a) See p. 96 (loop = ventral segment) and p. 102.
(4) (1) See p. 92.
(2) See pp. 103 and 104.
5. If the stem of a tuning-fork is pressed against a table, the sound is much louder than before.
(a)  Explain this and (b) give as many illustrations as you can of the same principle.
(e) Will the tuning-fork vibrate for a longer or shorter time when pressed against the table than when held in the hand. Am. (a) See p. 123 and p. 186.
(b)  String and sound-board. See p. 186. («) See p. 64.
1896.
Morning. 10 to 1.
1.    How has the velocity of sound been determined (1) in air, (2) in water?
Am. (1) See page p. 270.
(2) In a similar manner. The sound was made by a hammer striking a bell under water, the same lever which moved the hammer igniting some gunpowder above. The sound through the water was perceived by lowering into the water the wide end of an ear trumpet covered with membrane and turned towards the direction of the sound.
2.    Describe fully the apparatus you would use, and the mode in which you would use it, to prove that the frequencies of C, E, and G are in the ratios of 4 : 5 : 6.
Am.—See Helmholtz' Syren, pp. 33, 34, and 45.
3.    A steel wire, density 7*8 is stretched by a weight of 39 lbs. and gives a note of frequency ». A string, density 1, has double the length and double the diameter of the steel wire. "With what weight must it be stretched to give frequency n
T
Am.—Let I and d denote length and density of steel wire, and let z denote weight required then, from p. 87
y/39_______   _ yA
I X d X /—             I X d
V 7-8
V x                              v x
and -s
2             2<!X2rfx
y]
          4: iXd