The noise-cancelling headphones you use to shield yourself from babies, traffic, annoying spouses, and other sonic nuisances, are all powered by a single mathematical formula, Wired explains: the Fourier Transform. Sounds are waves. The Fourier Transform analyses a given wave, and produces the equivalent of its audio opposite. When that’s played, the two more or less cancel out, muffling your audio environs. Think of it as bizarro Superman punching Superman in the face. [Wired]
Matt
Saturday, May 28, 2011 at 10:11 PMThis article is all kinds of wrong. The Fourier Transform converts a signal from the time domain into the frequency domain, it has nothing to do with ‘generating an equivalent audio opposite’…
Charbz
Sunday, May 29, 2011 at 10:36 PMThat’s just incorrect. The fourier transform allows you to recognize the frequency components in a signal. By producing the negative of each frequency component, they are effectively canceled out.. The fourier transform is a mathematical tool so signals can be operated on in the frequency domain rather than the time domain, it’s not just a noise cancellation method. The production of a negative to the ambient noise is done in the frequency domain, superimposed on the original signal and and inverse fourier transform is performed, giving the illusion that the noise is blocked out. This is done on the fly so changes in ambient noise are also canceled out
Nodeity
Monday, May 30, 2011 at 9:11 AMErm… yeah,… what he said… I think,… wait,… what…? :)
olearymo
Monday, May 30, 2011 at 8:59 AMMatt and Charbz, seeing as you both seem to know about this…
Is it possible to use this technology to ‘silence’ helicopter blades and plane engines?
If not, why not? Have always wondered.
noober69
Tuesday, May 31, 2011 at 2:39 PMNo you cannot cancel out a helicopter blade.
The noise is generated at a point (or multiple points) and spreads out at the speed of sound. Think of a dripping tap causing ripples. While you can try to generate an inverse, you would have to generate the inverse in exactly the same spot at exactly the same time to cancel out the noise effectively. This is impossible. Headphones work as they are only trying to cancel out the noise in a very small location: your ear. For example we have all seen water waves from two drippping sources interfere. At some specific location the waves will cancel each other out.
Nodeity
Wednesday, June 1, 2011 at 8:52 AMThey have however built very quiet choppers by feathering the tip out at an angle to the blade. One was used to gain quiet access to “Osama”…
TK
Monday, May 30, 2011 at 1:56 PMIs there a formula to cancel out lady gaga?
Jake D
Monday, May 30, 2011 at 6:55 PMTriple J
Nathan
Tuesday, May 31, 2011 at 12:00 PMUnfortunately the formula doesn’t extend to Kanye.
jasonk
Sunday, June 5, 2011 at 8:50 PMI can’t believe the lack of fact checking or science on this blog. Anytime something technical come up, it’s only half right. Makes me wonder how correct the content is that I’m not an expert in.