What is a Phase Cancellation?

[imdookieatmaster]

Can someone tell me in detail what phase cancellation is, and what it is used for? And the benefits of it? Thank you very much.

[tribeofenki]

when the two summed signals have same and opposite values at the very same time... well, s**t happens.
NOTE: This is a gross no-technical answer.

[dannygold]

Glossary: Phase Cancellation | Sweetwater.com

[imdookieatmaster]

i604 I had a question, how can you have the very same signal at the same time and being opposite, could you help me with an example?

So when you say two summed signals lets say I have a vocal on the left channel, and the SAME vocal on the right channel and it is the SAME exact vocal that's phase cancellation?

[tms8707056]

See the links below. This is a principle of audio that cannot be easily understood without a solid understanding of the basics.

Sound - Wikipedia, the free encyclopedia
Digital audio - Wikipedia, the free encyclopedia
Waveform - WikiAudio
Phase - WikiAudio

[NorseHorse]

Don't forget. With digital audio, you can COPY and PASTE.

So you can have the exact same audio:

a. 1010101
b. 1010101

If you invert the "phase" of the second copy, the ones and zeros cancel:

a. 1010101
c. 0101010

(No folks, I'm not using actually binary, just ones and zeros...)

[imdookieatmaster]

Wait that's polarity no? When you get a song.


And flip the song isn't that pulling out the vocals or something like that?

[MrT]

When you sum waves you are making a Superposition. i.e. adding the values together. Phase refers to the relationship between a wave and time. SOooo... When you combine two waves from the same source (say two mics on a guitar), by vertue of a small delay in the time it takes the same wave to be recorded on two or more different mics the peak of one wave can correspond with the trough of another. So lets just say the amplitude of the first wave is +1; at the same time the bottom of the other way is -1... add them together and you get '0.' So that would be perfect phase cancellation. And you can get any combination in between.
Like This:

or This

Now throw on top of that the fact that the wave made by a guitar (or say a cymbal) is not a perfect sine but a combination of many waves at many frequencies and you can get some pretty funky shit going on. This usually presents itself as "wishy washy" cymbals or a guitar track that sounds good when each mic is solo'd but sounds filtered when they are combined.
Like This:


There is more to it but that is as simple as I can put it right now. This is more or less just basic physics stuff. If you click on the THIS it will take you to a page that explains this in FAR greater detail than you will ever care to know.

[imdookieatmaster]

So phase cancellation simply means that you'll get horrible sound, and lose good sound right? So like when an engineer says, "we don't want phase cancellation"
he just means, we don't want distortion or ugly sounds.

Right?

[jdg]

no, it means, he doesn't want the phase to cancel between the signals.

if the audio could be represented by the number 1 in one channel, and the number -1 in the other channel. when these two audio signals happen at the same time. you could have some phase cancelation.

[imdookieatmaster]

What is bad about phase cancellation, why would we not want it?

[MASSIVE Master]

Because you don't want sounds canceling each other out. Are you not reading the information people are providing you?

[Winey]

Shtick - Wikipedia, the free encyclopedia

[jdg]

phase cancelation its not bad unless you dont want it.

[Paul Gold]

If you have a single sound source being picked up by two microphones and you have your girlfriend move the microphones around for an hour or so you will experience cancellation.

[imdookieatmaster]

Massive is helpful now. Thanks bro

[flatfinger]

Some Nice info in a somewhat unexpected place...


SYNTH SECRETS

Combining complex 'out of phase' signals does not necessarily lead to complete cancellation. In fact, in the real world, it rarely, if ever, does so.

So many examples show simple sine waves, this gives you the building blocks , but as usual , there's lots more going on. The moral of the story is move the mic around and use your ears!

[tribeofenki]

the very same signal at the same time, being opposite, gives 0 (cancel),
But some asymmetrical situation, as the ninfty 3rd animated image above, gives somewhat a new dynamic dimension to the sum.

It is you that sum the signals, the right signals give totally unexpected results, even 0 or total mess...

[wheatus]

record a single audio tack

copy and paste it to another track in grid mode so that it has the exact same time stamp/location in the time line as the original.

invert the phase of the 2nd one

make sure you have no discrepancies between them ie, different panning, lugins, comp, eq etc...

bring the fader up on the copy pasted track until it matches the volume on the original track.....and listen to what happens.

Then you will know.

brendan b brown
wheatus.com