Interference Demo: Out-of-Phase Speakers

This is a demonstration of destructive interference produced by speakers that are out of phase with each other.

This demonstration was created at Utah State University by Professor Boyd F. Edwards, assisted by James Coburn (demonstration specialist), David Evans (videography), and Rebecca Whitney (closed captions), with support from Jan Sojka, Physics Department Head, and Robert Wagner, Executive Vice Provost and Dean of Academic and Instructional Services.

[happydappyman]

wow this videos is a remix waiting to happen. Thanks for the upload!

[alistairstuart]

Thank you for making this video I found It interesting, I never knew that having speakers wired the wrong way could have this affect

[carlosdrummer]

This video helped me finding a flat spot in my room that I was not aware of, I have two Homepods mini configured as a stereo pair, and the in-phase tone sounds very thin when my head is almost exactly mid-distance from each speaker, but sounds full-bodied everywhere else in the room. Don’t believe the Homepods are out of phase with each other, so it’s very strange.

[stevefisher]

The speakers are right next to each other with a 100 Hz tone, so there can be cancellation with the omnidirectional soundwaves at this frequency. This should have been demonstrated with the speakers apart as would be in a normal listening situation. This "test" would also have very different results at mid to high frequencies.

[djijspeakerguy]

It’s important to point out that interference like this is only going to happen when only one speaker has its polarity flipped. If both speakers have red to black and black to red, the system would actually work properly!

[Kevinb]

What I hate most about out of phase speakers is the sound feels like it’s in my head. It’s a very odd an weird feeling

[SidMed]

My car speakers when I play a phase checker the out of phase doesn't have any sound. Is it wired correctly?

[genesmith]

Experts who design and install professional sound systems have polarity switches on the huge bass subwoofers. Sometimes out-of-phase has more bottom. It has to do with standing waves in the room and more importantly how many people are there absorbing sound...

[aravindakumar]

Sir, if there is a source of noise and we want to nullify/reduce noise by creating a counter-noise with shifted phase which causes destructive interference; what device helps us to generate this counter-noise? Or, in other words, how to create a counter-noise practically to cause destructive interference?

[duroxkilo]

thank you, great demonstration. the terminology is not quite proper:
this was an example of a 'completely' out-of-phase configuration (180 degrees) resulting in max. destructive interference. it is better named 'reversed polarity'.
reversed polarity is always 180degrees out-of-phase..
out-of-phase can be anywhere between 1 and 359 degrees. (90 degrees out-of-phase is not 'reversed polarity' but it can also lead to destructive interference.)

*w/ sound, phase is frequency dependent, polarity is not.
the interference of two 100Hz sine waves shifted 60 degrees out-of-phase is different than the interference created by two 80Hz sine waves shifted 60 degrees... (when the phase is shifted 180 degrees, the interference is identical regardless of frequency as it cancels out)

[rvz]

So red to red, black to black..whhhoaaa

[alecreations]

would like but that would ruin the 69 likes haha so edgy wuu

thank you for the easy a extremely useful information