In physics, sound is a vibration that typically propagates as an audible wave of pressure, through a transmission medium such as a gas, liquid or solid.
Doctor: It plays music. What's the point of that? Oh, with music, you can dance to it, sing with it, fall in love to it. Unless you're a Dalek of course. Then it's all just noise.
Doctor Who Evolution of the Daleks (2007), written by Helen Raynor.
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