It is necessary to put the vibrating body in the vacuum - and the sound disappears, despite the fact that the body continues to fluctuate.

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This is easily seen by placing an electric bell under the glass globe and evacuated. Clearly visible from the hammer blows of his cup bell will not cause a sound.

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But if you let the air under the bell, the sound will be heard again. The particles of air set in motion by an oscillating body, convey their movement sequence to other particles. Deviation of the vibrating body, such as the right of the middle position, causing compression of air to the right and left of his thinning body. The next time the body starts to move to the left, squeezing with a layer of air adjacent to the left and right of the body will vacuum. Particles of air coming into the movement, will be exactly repeated vibrations, committed body and transmit them to neighboring particles of air. As a result, the individual layers of air are periodically compressed and discharged.
 Even more clearly the wave on the water surface. They seem to us as moving series of alternating ridges and troughs. Such waves can be created on the surface of water, for example by means of a float tied to a string. If the float begins to waver, then it will go from a circular wave. The particles of water does not move with the wave, and only fluctuate up and down.