Exactly what I was looking for, thank you.

Interestingly, the wavelength of sound and the wavelength of wifi signals are in the same ballpark. 900MHz electromagnetic waves come out to ~30cm waves, which is about 1000Hz in sound-in-air.

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lawlessone 4 days ago | parent [-]

just my lay person thought here.

But if you could cancel the noise/signal perfectly and everywhere wouldn't that sorta violate energy conservation?

The sound energy has to go somewhere right?

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loa_in_ 4 days ago | parent | next [-]

You are providing the energy by emitting the counter signal in the first place.

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card_zero 4 days ago | parent | prev | next [-]

That's an interesting question: what to do with the energy, ideally? Maybe convert it to very low frequency, so it only annoys elephants.

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luke-stanley 4 days ago | parent | prev [-]

Perfectly? Surely that is not reasonable?

	▲	IAmBroom 3 days ago \| parent [-]
		Even imperfectly, the problem remains - and is answered by the "the energy of the cancellation source counterbalances the noise energy."