HANDBOOK OF ACOUSTICS - online book

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286                    HAND-BOOK OF ACOUSTICS.
(b) As the man walks to one of the organ-pipes, more sound-waves per sec. from that pipe will enter his ear than if he were at rest, because he advances to meet them. On the other hand, fewer sound­waves per sec. will reach his ear from the other pipe. One pipe will consequently appear sharper than the other, and therefore slow beats will be heard.
7.  (a) Explain the formation of combination tones.
(b) Why is it that in the case of some instruments these tones can be reinforced by the use of resonators, while in other cases resonators are of no assistance ?
Am.(a) See pp. 133 and 134.
{b) When the same mass of air is agitated by both generators as in the case of an harmonium bellows, the combination tone has an objective existence and can be reinforced by resonators. In other cases the tones are subjective, formed in the ear, and cannot be thus reinforced.
8.  (a) Distinguish between exact and tempered intonation, and describe the system of equal temperament.
[b) If the pitch number of C is 264, what will be that of A—(1) in exact; (2) in tempered intonation. Ans—(a) See pp. 238 to 241.
(b) (1)                T Xl = 22°
264 / •»/ \s 264 */
(2) — -i- ( V 2) = -f -f- V 2 = 222
UNIVERSITY OF LONDON.
Intermediate Examination for Degree of Bachelor of Music Tuesday, December 14, 1898. 10 to 1.
1.   (a) Explain why the interior length of a stopped organ-pipe is approximately equal to one quarter the length of the wave of sound which it limits.
(b) Why is it not precisely equal thereto ?
Ans.—(a) See pp. 61 and 62.
(b) See answer to 4* Mus.Bac. (Cambridge) Exam., 1899.
2.    In what way is the pitch of an organ-pipe affected by changes in the temperature and in the humidity of the air.
Ant.—See pp. 100 and 101. The greater the humidity the sharper the pipe.
3.  (a) State the ratios between the frequencies (i.e. vibration number) of any fundamental note and the frequencies of the seven successive notes of its major scale (untempered) up to its octave.