sound cancelling sound

[frankbough]

Is it possible to make one sound cancel out another sound, to create silence?

[Flurfl]

Yes

[fo3nix]

basically, waves have a general, intrinsic, property known as "superposition".

sound can be perceived as a wave, so it obeys the superposition property. what this property means is that if you have two waves, they add together:

wave1 + wave2 = wave3

pretty simple right? well that's it. now, if you make wave2 exactly equal but oppesite "sign" to wave1, you get this:

wave1 - wave1 = 0

that is fundamentally how noice-cancelling technology works.

[Gef]

No.

[fo3nix]

Gef: was that "no" relevant to anything? Because if it was an answer to frankbough's question, your answer is incorrect.

[jake-the-peg]

To you $50

http://www.amazon.com/exec/obidos/tg/detail/-/B00005M1UY/102-0835560-0954542?v=glance

To paraphrase a certain Dlibert cartoon - "I have an idiot cancelling monitor but sometimes I can't read some of the answers around here"

:c)

[Gef]

Sorry fo3nix. You are (almost) correct as far as pure frequencies are concerned. For sound I read noise and although theoretically possible practically it would be impossible because of the range of frequencies.

[kempie]

Gef - Can't believe that this has resulted in such debate. One sound can cancel out another sound, end of story.

[Space]

You can create silence locally with that kind of headphone ( although I'm not sure that they are efficient at removing high frequencies )

But if you want to completely cancel a sound, so that it can't be heard anywhere, without needing to supply headphones to everyone, then it might be a bit more difficult...

[phl666]

you could place a microphone near the sound source, invert the phase of the sound, and play it back simultaneously, thus cancelling the sound.

[MargeB]

That would be impossible to achieve, because sound travels in waves, and the cancelling wave would have to be sent to just the right point at all times, an impossibility.

[MargeB]

Nice article in today's Times (a good read for once) about a new device called the 'mute'. Scientists believe it could reach the shelves within a year, however the advanced version, with 'Mother-in-Law' capability, is at least a decade off.

[Gef]

Kempie - it can't, sorry.
At the moment my neighbour is playing loud music. There is no simple way to cancel this out.

[Personica]

Gef. sound waves are merley disturbances of air.

Take the example of your neighbours music.....

His speakers contain a diaphragm which 'punches' the air around him at variable frequencies to create noise.

To cancel the noise, simply enter the air around his speakers and punch him with an eaqual frequency, until the noise is cancelled. Experiment Completed :-)