Acoustics & Sound For Musicians - Online Book

The Theory Of Sound Which Constitutes The Physical Basis Of The Art Of Music.

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	I. § 21.]          TRANSMISSION OF PULSES.                  43 i.e. diminution of pressure accompanies diminution of density. By experiments such as the above it was shown, by the French philosopher Mariotte, that the pressure of air varies as its density. 21. Next, let us take a cylindrical tube open at one end and having a movable piston fitting into the other, as in Fig. 19. In (0) the piston is at rest at A, and the air in its ordinary atmospheric condition of density and pressure. In (1) the piston is pushed inwards as far as C. While it is moving up to this position, the air-particles in front of it are thrown into motion.
	Suppose that, at the moment when the piston reaches C, the particles at D are just beginning to be dis­turbed. The air which, in (0), occupied AB is now crowded into CD, and is therefore denser than that further on in the tube. Next, let the piston be