The Science of Silence

What with all the high drama over healthcare reforms, global warming, H1N1 flu and economic collapse, isn't it time to think about something good... something pure... something lovely? How about oh, say, pipe organs?

A group of physicists at Potsdam University in Germany are doing just that. Using the tools of fluid dynamics modeling and nonlinear science, they're investigating an age-old mystery.

Physics Buzz, the blog of the American Physics Society, describes the mystery like this: "...when two almost identical organ pipes are played side by side, something strange happens. Rather than each blaring their own tone, the two pipes will barely make a whisper. But put a barrier between them, and they sing loud and clear." The question, of course, is -- why?

What the group learned is that nearly identical pipes positioned next to one another are tuned to such similar frequencies that their slightly out-of-synch sound waves nearly cancel one another out. Organ makers, of course, knew this intuitively though they couldn't explain the phenomenon, and as a result they have always placed pipes of similar sizes far apart from one another.

Following up on this discovery, the Potsdam group conducted more experiments. They found that even the tiniest signal from a loudspeaker can cause an organ pipe to go silent, if the frequency is identical.

Digging even deeper, they found "synchronized canceling could work for noises that peak at a certain frequency; for instance, pipes fitted into an airplane's wings could silence the deafening roar of its engine during take-off or landing." A similar approach could work in factory settings or other areas where irritating sound reaches a predictable frequency.

What does all this research tell us? In the long run, it may provide a low-cost, high impact tool for the creation of peace and quiet -- in a world of chaos and unfettered noise.

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