What Does Acoustic Interference Look Like?

No video

What Does Acoustic Interference Look Like?

Рет қаралды 46,248

Harvard Natural Sciences Lecture Demonstrations

4 жыл бұрын

We use the strobing schlieren effect to visualize acoustic interference between two 28 kHz sound waves. Recognizing where constructive interference must take place allows us to interpret bright bands of light that appear in the continuously illuminated schlieren image.
Special thanks to Dr. A. Klales, who first suggested we try this experiment, and also thanks to J. Peidle, for showing us how to externally trigger the strobing LED!

Пікірлер: 98

@zakolia 4 жыл бұрын

Shlieren effect and standing waves is a super fascinating mix. I would really enjoy playing with the possibilities.

@bookdream 4 жыл бұрын

This is fascinating and beautiful, I want to see more sound waves and fluid dynamics with this imaging technique.

@choppps5858 3 жыл бұрын

Looks like real magic. Totally impressive

@Zeno2Day 3 жыл бұрын

Excellent demonstration

@shawnphillips4804 Жыл бұрын

Absolutely amazing!

@backonrun626 Жыл бұрын

Wow this was very educative

@patiram5439 3 жыл бұрын

Nice project

@davidnikon8501 3 жыл бұрын

I love learning from you.

@treyharper7885 4 жыл бұрын

Wow, so fascinating! Thank you very much, you're an excellent teacher.

@wolfgangrueckner7151 4 жыл бұрын

thank you

@MrEstebanEscudero 4 жыл бұрын

Great video!

@GlutesEnjoyer 4 жыл бұрын

amazing demonstration. thank you!

@il_vero_saspacifico6141 3 жыл бұрын

Soooo cooolll

@maitland1007 4 жыл бұрын

Pretty nice mirror you have! Thanks for the video.

@IronMoe 2 жыл бұрын

this is very nice

@hawkfpv1636 3 жыл бұрын

Reminds me of the double slit experiment

@cheyennealvis7899 3 жыл бұрын

yup. follow that line of thought and you'll come to an amazing realization. But if you tell people they'll laugh at you. So it's better to just give them the bread crumbs they need to help them figure it out themselves.

@ed-xs3pu 3 жыл бұрын

That light is only a wave and the particle theory was to cover up the fact that they couldn't admit they were wrong?

@realamerican6161 4 жыл бұрын

Wonderful experiments.. I would like to see the two emitting sources placed into one-another. Placed in such a manner that the position of the 2nd emitter may be adjusted spatially so the node/anti-node can coincide with the 1st. Much the same as you did with the glass plate. I enjoy the videos Wolfgang...

@wolfgangrueckner7151 4 жыл бұрын

Thank you. We'll try aiming them at each other some time in the near future.

@funnycatvideos5490 3 жыл бұрын

Light looks exactly like this when I leave my light on, through a slit in my bedroom door. Awesome that could definitely explain the double slit, just pressure mediations in the medium, nothing is being emitted lol.

@nickplaysviola 3 жыл бұрын

this is so good, thank you

@adrianskotniczny5413 3 жыл бұрын

nice job

@MrJdcirbo 4 жыл бұрын

You didn't talk about destructive interference, where crests meet troughs. That's part of the interference pattern. Otherwise, awesome video! I love how the strobe frequency created the illusion of a standing wave. Brilliant!

@wolfgangrueckner7151 4 жыл бұрын

thank you

@smokysmoka 2 жыл бұрын

💙

@AbeDillon 4 жыл бұрын

If you offset the frequency of one of the transducers by 30-60 hz would the camera pick up the beat frequency?

@NatSciDemos 4 жыл бұрын

In principle it could be done, but as a practical matter it would be complicated by the fact that these particular transducers do not give a constant power output for all frequencies.

@kguy152000 4 жыл бұрын

Wow

@shamsulalamdhaka 4 жыл бұрын

Nice. Thanks.

@ccc321321321 Жыл бұрын

Hello, professor, the video uses this method to see the movement behavior of waves in the air. Is there a way to see the movement behavior of the transducer?

@NatSciDemos Жыл бұрын

The transducer moves under the influence of a sinusoidal current, just like a transducer in, say, a stereo speaker. Because it's driven near resonance, the phase between the motion and input current will differ by about 90 degrees. Viewing the motion visually could be done using a very fast (approx 28 kHz) strobe light, but it would still be difficult to see because of the small amplitude.

@shaunlewia9710 3 жыл бұрын

has a variation been tried with the double split experiment, to me it seems the wave forms are partictice when one transducer observes the other, and by the end we see everything is a wave. just time and case for observer for items to become solid. Blown my mind

@wolfgangrueckner7151 3 жыл бұрын

Unhappily, our mirror is not large enough to do a double slit type experiment.

@ed-xs3pu 3 жыл бұрын

The double slit experiment is the lightwave version of this. It has been falsely claimed to prove light is a particle, but we see quite obviously that it's just wave interference.

@karlharvymarx2650 3 жыл бұрын

The sound is ultrasonic, so by definition I can't hear it and even if I could, the audio is low pass filtered at about 15.5kHz. Yet I can hear something when the emitters are running. To verify that I'm not hallucinating, I downloaded the audio and had a look at the FFT. They really do seem to be producing extra sound, strongest at roughly 14.25kHz and 14.6kHz. I have noticed the same thing using cheap piezo buzzers to play with ultrasound at home. Is it caused by alternate vibration modes in the emitters, rattling, or something else? It is loudest at the et the end of the video.

@wolfgangrueckner7151 3 жыл бұрын

The transducers are known to also emit sub-harmonics

@xxcood 3 жыл бұрын

Hi there, it waz very interested to see some with a real knowledge about an idea that came to me since 10 years, and i wonder if you get with your knowledge to the results i did, but i couldn't deploy it because i was not my bath and also i didn't have the resources, you did mention about the levitation an opject with a sound wave, did you ever consider for levitation the source of the sound with those waves?

@cheyennealvis7899 3 жыл бұрын

he solved the problem relating to quantum mechanics and the double slit experiment and the nature of particle vs wave without even knowing it lol.

@geoffrygifari4179 4 жыл бұрын

i think its remarkable that transducers shoot up sound waves that go somewhat in a straight beam instead of diffracting outwards

@wolfgangrueckner7151 4 жыл бұрын

It's because the transducers a flat and not a point source. The waves do diverge because the flat areas are not all that large.

@geoffrygifari4179 4 жыл бұрын

@@wolfgangrueckner7151 for how long do you think the waves would not diverge? several meters?

@wolfgangrueckner7151 4 жыл бұрын

@@geoffrygifari4179 Generally speaking, waves diverge from their source by the ratio of their wavelength to the diameter of the source. In our case the wavelength is 12 mm and the transducer diameter is 45 mm. Thus, 12/45 = 0.27 radians, or about 15 degrees. And that's pretty much what we see in the video.

@ScientificSolutions 4 жыл бұрын

Very nice, thank you for sharing this new video! What I would like to know is, from one of your earlier videos in which you suspend balls on the standing waves, are you able to feel (with your finger, or a wand of sorts, etc) the compression zone boundaries?

@wolfgangrueckner7151 4 жыл бұрын

No, I don't feel a thing with my finger.

@zakolia 4 жыл бұрын

Wolfgang Rueckner hmm.. maybe you should see a medicine doctor!?

@zakolia 4 жыл бұрын

That's a question I had in mind for a long time, thanks.

@wolfgangrueckner7151 4 жыл бұрын

@@zakolia I believe most human body senses require a stimulus of the order of at least 1 millisecond long, or longer. 28 kHz has a period of 37 microseconds.

@zakolia 4 жыл бұрын

Wolfgang Rueckner wow! That's a great answer, thanks a lot. But I meant that as a joke: don't feel A thing with your finger... Thanks for your professionalism.

@mark5150ty 3 жыл бұрын

Has anybody tried using infrasound with this setup?

@zakolia 4 жыл бұрын

Can you show gradually decreasing sound frequencies with corresponding strobe frequency? We could see the waves stretch appart.

@wolfgangrueckner7151 4 жыл бұрын

I'm afraid we can't do that with our transducer because it's a fixed frequency. Otherwise, it would be possible.

@zakolia 4 жыл бұрын

Ok, thanks for answering. I really like your videos

@wolfgangrueckner7151 4 жыл бұрын

@@zakolia thank you

@zakolia 4 жыл бұрын

@@wolfgangrueckner7151 I mean, we could tell if the sound waves are quantized. Streching them apart hertz by hertz and see if it jumps straight to the next position. I would love to play with your contraptions!

@WakarimasenKa 4 жыл бұрын

The troughs interacting with each other would also be constuctive intereference, right?

@wolfgangrueckner7151 4 жыл бұрын

correct

@WakarimasenKa 4 жыл бұрын

@@wolfgangrueckner7151 thanks

@primodernious 3 жыл бұрын

in theory you chould be able to levitate a small object with only two transducers in this configuration.

@wolfgangrueckner7151 3 жыл бұрын

correct ... and many people do it that way

@deilusi 3 жыл бұрын

rotate it 90' and add those tiny balls for extra effect.

@fattmouth7715 3 жыл бұрын

Love it. Problem is the guy's voice puts me to sleep.

@tristang444 4 жыл бұрын

Could you rotate the pair of transducers so we could see it three dimensionally?

@wolfgangrueckner7151 4 жыл бұрын

In principle, that could be done. In practice, that would be extremely difficult with our present set-up.

@rogershanklin3210 3 жыл бұрын

Why can we see the constructive interference, but not the actual, or whole(?), wave?

@NatSciDemos 3 жыл бұрын

To see the constructive interference, we use continuous illumination. We don't see the traveling waves under continuous illumination because they move very fast (the speed of sound is about 340 m/s).

@websonic1000 3 жыл бұрын

HI, It would be great if you would oblige us to do experiment with double slit experiment with your setup.

@wolfgangrueckner7151 3 жыл бұрын

We need a larger mirror to do that ...

@websonic1000 3 жыл бұрын

@@wolfgangrueckner7151 Pitty, Have this feeling that Schlieren effect could show us what is happening with light beam before entering one of those two holes and after.

@labbeaj 2 жыл бұрын

Looks like the clouds above our heads.... Especially, if the Nexrad Radars actually are manipulating the clouds instead of predicting them.

@axelvf1981 4 жыл бұрын

Great video! I'm working on a project where we are looking for someone to visualize three different acoustic frequencies with schlieren photography. Would you be able to help us? We would of course be able to reimburse for your work.

@wolfgangrueckner7151 4 жыл бұрын

I would need to know more details (concerning what you want to do and see) to know if I can help you.

@axelvf1981 4 жыл бұрын

Of course! Can i send you an email?

@wolfgangrueckner7151 4 жыл бұрын

@@axelvf1981 Certainly. It's ruecknerw@gmail.com

@johannesdeboeck 4 ай бұрын

This sounds very interesting. Did you manage to do this?

@patiram5439 3 жыл бұрын

Easily found slowly bites 2.8 2.8 2.8 speed

@indiarajasthan4707 4 жыл бұрын

Yahooo

@SuperDatsun71 3 жыл бұрын

Nikola tesla said this if I'm not mistaken already

@vladmatsala9753 3 жыл бұрын

How does that mirror work? Is that some camera mode?

@wolfgangrueckner7151 3 жыл бұрын

It's a concave 2-m focal-length telescope mirror

@vanotank1645 4 жыл бұрын

даёшь такой опыт на 2 щелях

@AbeDillon 4 жыл бұрын

Why does ultrasonic sound travel so linearly?

@NatSciDemos 4 жыл бұрын

The waves are seen to spread out only a little bit in the picture because the transducers are flat surfaces and we're looking at a very close area around them. In other words, if the transducers were more like point sources then we would see the waves radiate out at a wider angle.

@AbeDillon 4 жыл бұрын

@@NatSciDemos That makes a lot of sense. I've heard that higher-frequency sounds travel more linearly than radially, but it makes much more sense for that to be a consequence of the transducer than an inherent property of high-frequency waves.

@j3ckl3r 3 жыл бұрын

I want to see what happens when you try to levitate a ball in it

@tamaseduard5145 4 жыл бұрын

Thank you sir 👍🙏 I remain to my idea that the formula of energy is this: ENERGY = ( ETHER / MATTER ) X ( RATE OF CHANGE )

@GTAVBM 3 жыл бұрын

This explains how ancient megaliths were moved around in the past.

@lalitpal9302 4 жыл бұрын

The sound/vibration of AUM is very important in Hinduism. In yoga the there is whole science behind sound/vibration. The whole universe is menifested in vibration/sound which is AUM as per Hinduism. AUM is base of all sound just like red, green and blue is the primary color in the world of colors . I wish modern scientists can explore more into vibration/sound.

@GPCTM 3 жыл бұрын

1:45 really?! an Harvard man stating the obvious? omg it's "simply because" the light travels at different speed in that region "simply because" the density there is different "simply because" the pressure is different and because of that temperature is different and density affects light speed...