Why can’t human voices be “out of phase”

[Bearitone]

Kind of a stoner question here but this has been on my mind:

I know I can wire two speakers out of phase and get destructive interference. Why can’t two human voices or singers ever be out of phase? Assuming no electronics involved regarding the singers.

 

[MikeH]

Either you're so stoned that the question doesn't make sense, or I'm too stoned to understand it...

 

[lost_horizon]

They have to be exactly the same, get one voice, split it into two channels and put it in a stereo amp and it will phase cancel.

It's a physical thing, they would have to be facing each other and if they hit the same note the same way from the different directions they would phase cancel in the middle.

 

[Grindspine]

Two human voices definitely can be out of phase.

 

[Hollowway]

I think any two sound sources can, but maybe it’s because there are so many small constructive and destructive changes that it’s not noticeable?

I’d think that if you had two people with similar timbres singing the same line in unison it would be enough be noticeable, but I don’t know enough about it to know. Now I’m wondering, too!

 

[Bodes]

Take my word for it, I've definitely heard many people's voices completely 180° out of phase with any form of coherent thought process.

 

[SalsaWood]

Oh boy.

Long answer very shortened would be that because human's aren't computers and cannot easily use pure tones in vocal tracks which would make it simple, and/or otherwise they still lack the collaborative ability to match or mismatch in regard to phase. Phasing, as you know, deals with the position of the waves relative to each other. Getting them to match or relate in much more than simple ear'd pitch is going to be a very tall order. They would need to tell the difference between a few hertz and be physically able to traverse those small offsets vocally.

You'd need to be the two most talented vocalists the world has ever seen and they'd need to be specifically trained to do so. I think it's generally possible, but not perfectly. Their offsets would still probably very large and not especially useful musically.

 

[TedEH]

Assuming no electronics involved regarding the singers.

This is your answer right here. Humans are not machines, and sound works incredibly fast. Any two sound sources can (and do) interfere with each other, but humans aren't that precise. You would need two people with exactly the same voice producing exactly the same sound at exactly the same time. Then they would cancel. But it's like asking two people to freehand draw circles while blind, and hope that they draw exactly identical circles, such that if you overlaid them it would be the same drawing, also they have to do it at the same time. It's not teeeeeeechnically impossible, but it's so phenomenally unlikely it might as well be impossible.

 

[tedtan]

For something to be completely (e.g., 180 degrees) out of phase and cancel with something else, it has to be two identical things with one of those thing’s phase flipped, like copying a recorded guitar or vocal track guitar to another track, setting the volumes equal on both tracks, and then flipping the phase of one of them. If you have two separate tracks, like a doubled guitar or vocal wherein you have two separate performances, and then flip the phase on one of them, they won’t cancel completely because the performances aren’t identical.

If you have two separate singers, even if they have very similar voices, they won’t ever be the same performance, so you won’t get complete phase cancellation.

But you will get partial phase cancellation, which is actually pretty common and not a problem.