A text book of physics, for the use of students of science and engineering (1918)
Duncan, John, d. 1941, Starling, Sydney George, 1873- · London Macmillan · leaf 694
produce any sensationof sound. On shortening thefree part of the spring, thevibrations obviously becomemore rapid, and soon a lownote will be heard. Withfurther shortening, the fre-quency increases, and a noteof higher and higher pitch willbe heard, until, when the springis something like 1 cm. in… … Fig. 614.—Disc siren. 670 SOUND CHAP. A disc having two circles of holes in it is capable of being rapidlyrotated, and a tube A, leading from a pair of blowpipe bellows, directsa draught of air against the holes. When the rotation is very slow,a puff of air passes through each hole as it comes…
Physics
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