Interference Demo: Speakers

This is a demonstration of the interference pattern created by two speakers playing the same 2000 Hz tone. It is carried out by moving a microphone through the sound field and noting that the sound is louder in some spots (those with constructive interference) than others.

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.

[parjitkhakh]

Seeing and understanding how the waves cancel due to superposition from the book is one thing but actually hearing, or the lack thereof, the sound cancelling is incredible.

[mszuri]

Actually seeing a demo makes the book word problems make more sense. Appreciate it.

[simonmoore]

How amazing, a whole world of physics invisible to the naked eye but able to be perceived by our other senses. Thank you so much for the demonstration!

[ajeyhegde]

I had thought that such a thing wouldn't happen in reality but after viewing this demo, got convinced with things. Thanks a lot!

[gayatri]

My favourite channel for physics, it makes the content written in the book living and real...

[kevinpolpitiya]

Thanks for the demo. Due to the lockdown we are unable to perform these experiments individually. Hence we must rely on videos on YouTube. It was difficult finding a decent video to represent this topic. This was great!!! Thankyou!!!

[r.a.]

This is the sound variant of the double slit experiment. Awesome.

[manjumeo]

My physics teacher ask us to watch it, really amazing explanation 👍

[creatureofvenice]

Thank you so much! This is the best video I could find for this!

[nehemiahshird]

THATS MY SCHOOL!!! UTAH STATE UNIVERSITY!! GO AGGIESS

[kristyevans]

saw an explanation video 1st.. didn't get it..searched for some other explanation video but got your experiment video and man I didn't know it was so easy to understand

[djijspeakerguy]

I’m pretty sure this interference is called comb filtering. If you move around while playing pink noise, you’ll hear certain frequencies start to pop out, and a sweeping noise as you move. Sitting in the exact center in a concert, for this reason, will usually sound the best by far. It is worth noting it has to be the exact center.

[BrentMurrell]

nice soothing tone you chose there lol — thanks for the demo, really appreciate you

[occultbass]

Life is crazy! The fact stuff like this exists is crazy! You are very intelligent!

[prateek]

loved it soo much cant tell you, i was struggling from a long time to understand interference because its boring as hell.but you proved today that it could have been so interesting.

[pubs]

Love Mr. George Kafentzis, best physics teacher EVER. Hope I pass your exam tomorrow :P

[sam-hkru]

Wow that's amazing to understand an gorgeous experiment

[tennicktenstyl]

That's why headphones are superior

[ramennight]

Thankyou! I've understood what interference has done to waves, but not what that means to me in the practical sense.

[sikretp]

thank you for sharing the insightful knowledge.
👏👍✨