I Made a Lens, But for Sound 

I forgot to say "refraction" at any point during this video! So yeah... "refraction". Thanks for the idea Zach!

Next video: acoustic lasers, using modulated ultrasonic speakers

Oh gosh ! It opens up so many possibilities. I'm thinking : can we make a sound prism ? That could be a way to do some kind of physical Fourier transform. Idk, my knowledge is lacking in this field.

Steve's wife: Shall we sort the garden out. Steve: Yeah, gimme a minute.

Just today I read an article about sulphurhexofluoride, which is today's most potential green house gas in use. Until 2005 it was used in sound dampening windows panes. I wondered how it works, but didn't bother to look further into it. But now with your video it suddenly came to me that the heavy SF6 leads to total internal reflection between the glass panes, therefore converting the sound into heat. Amazing coincidence!

You are a dedicated man. I loved the explanation of the slower to faster wavelengths and the shapes of the lens that you showed. Everything you were saying instantly clicked in my head! What a cool experiment

4:04 my brain: "how do you make concave balloons?" "Blow concave breaths"

That was way cool. Thanks Steve!

5:47 You´re such a troll i love it

Can you expand on the project? Try and make a "beamed" sound that you can only hear if you are in line with the "beam"?

"ironically, it sounds just like a balloon deflating." Simon Cowell, is that you?

I mean you wouldn't be lying if you said click the link for 30% off

"Oh that thing? It's a youtube play button. Yeah. Got one of those?"

U make such good content mate :)

I found this video interesting and honestly encouraging. I never felt like I was very adept at studying physics in school or even in college, but I always wanted to be an engineer. It's explanations like this that lay out exactly how and why it works that has built my confidence to be an engineer in the aerospace industry today. Not once did you say "Snell's Law"; you just showed the behavior step by step, and that's how I learn best.

"I skewed the whole noice towards a higher frequency" ... So, a blue noice?

best quarantine activity is watching your videos. thank you.

I greatly appreciate how you not only explain the concepts, you also explain why and how those concepts work in terms the average person can understand. Technical jargon makes it hard for the layman to understand concepts. If everything was phrased in an easier way, I think there would be far more advancements made. Cheers Steve

This reminds me, my dad showed me just the other day that a campfire's smoke warps and muffles sound (such as that from a radio) quite a suprising ammount

Exactly the perfect kind of information I'll probably never find a use for, but somehow don't know how I ever lived without! I can already see my loved ones' boredom as I try to explain how awesome this is! Liked, subscribed, all that!

Honestly the more videos you make the more i feel like you're ending up on everything Vsauce used to do and forgot and now they only do random useless things. I love your stuff, it's both incredibly obvious from what school taught us in middle/high school but they also never bother to cover the wider meaning this explores, and thus we never notice this can even exist.

I had to do a double take on that very first scene. Steve SO used that specific angle on purpose.

Thank you for giving me a spectacular AHA moment. The visual explanation of refractive index made so many things clearer for me. There rest of the video was excellent and informative as well.

Yes!! I love Brave Browser also this was a really cool and unique video, thank you

My music teacher always said I was acoustically dense. Any relation?

"heres how i got the copper pipe in the balloon" *video of him ripping the balloon in reverse* XD

I taught physics for several years and I have never seen this demo. SUPER well done and I can't wait to try it!

I dont quit need a browser but I'd download it with your link cause channels like you helps me more to learn, thank you mate

Some of the loss of volume from the helium might also come from impedance mismatching, like you've covered in some of your other videos. I guess that would be the case too with the CO2, so the lensing effect is definetley stronger.

Tech Ingredients also has a really good video on sound isolation using helium gas

This is super fascinating! I was glued to this video while you were describing it.

Glad to see Brave sponsor quality content like yours. I've been using Brave for about half a year now and it's the best browser I've ever used.

A large part of the silencing effect of a helium balloon is due to impedance mismatching between air and helium due to the large difference in mass between the particles in each and the resultant poor energy transefer. The RU-vid channel Tech Ingredients has a great video on this.

Tech Ingredients did two videos on the acoustic properties of helium a couple of years ago. They include a number of interesting experiments.

Been using Brave for a while now, love it! Highly recommended!

Great job describing these concepts !!

Wait, but I thought sound travels *slower* in less dense mediums and *faster* in more dense mediums? I'm so confused.

The thing I find interesting is that the waveform after passing through the focusing lens seems to have some distinct peaks and troughs. It's hard to say just from a youtube video, but it would be interesting to see an actual analysis of the waveform, and why it seems to increase in amplitude only in some spots. Is this chromatic aberration?

Great video! The way you present the experiments has me working through the outcomes in my head, trying to predict the outcome. Definitely fun! Thanks...be safe!!

Fascinating stuff Steve, I wonder if this sound lensing effect could be utilised in speaker or headphone technology...

When you said it sounds quieter I just assumed it was because of the helium being less dense than air so it doesn't transfer the sound wave as well.

Steve: *tells about brave* Me: *already has brave* Me: *clicks link anyways for those money stacks for steve*

Great video, really enjoyed this practical application of some topics relative to my work!

Here's something about sound I learned in the Air Force, working on the flight line with dozens of running jet engines all around me. If I were to stand directly in the exhaust (in this case, its about 30 feet behind an F-4 Wild Weasel, at idle, with outside temp of about 20 degrees F) I could remove my hearing protection and not be bothered at all by the sounds of the other jet engines nearby. Stepping out of the exhaust and into the cold air would cause hearing damage. The jet noise on the flight line is about 130 - 140 db at idle. But on a cold day, in the exhaust, its about 65 db. A very big difference.

2:08 Oh my god Thank you so much for showing me that

here's something: even when walking with someone on gravel, i notice sound phasing/flanging when they're a few metres away. Same effect, as when you 'shhhh' at your own hand/a wall and come closer/further from it. try it out yourself, if you understood what i meant haha!

The best visual explanation of refraction I've ever seen!

Funnily enough, I was just wondering if this would be possible the other week (possibly after watching your last video?). And then I forgot. So thank you for A) reading my mind, B) not forgetting, and C) actually following through with it and explaining how it can work! Honestly now I just love the idea of making sound lenses for TV studios. Rather than having microphones right next to people (be they lavalier mics or the big boom mics they hold above people), they can just have a giant balloon full of a heavy gas like krypton to focus all the sound into a distant mic and keep the people on stage more free to move around. I doubt it would work properly but it would be so silly that I'd love to see it tried anyways

I do believe Tech Ingredients has discussed helium extensively in one of his soundproofing videos. He didn't use a lens shape.

1:08 I respect that flex 👏🏻👏🏻👏🏻

This is so interesting. Thinking of the all the potential applications of this in a professional audio/music situation, or to sculpt the sound of a residential environment to reduce train noise etc… good stuff!

thanks for using Brave! I love sending you tips

Could different gasses create audio filters? If you mix gases, could you essentially create an equalizer?

You might enjoy Tech Ingredients video on helium.👍

Glad to see you advertising Brave, I’ve been a long time fan and use it exclusively on mobile.

That's the best way I've seen for explaining how lenses change the direction of light. Mind blown!

Could one possibly visualize this via Schlieren imaging?

Hmmmm. There is a video about the helium thing on Tech ingredients, their explanation is a bit different.

All ur topics are very unique. Thanks steve

Awesome video! ...but two weeks too late. My physics class just finished optics. They will see this video anyway. One of the advantages of distance learning is that it is new to us so we can experiment to see what works. Videos backed by reading and exercises seem to be the way to go. So, Thank you Steve for making my job a bit easier. Stay safe.

This phenomenon of noise dampening is because of impedence missmatching between helium and air. (most of it i believe) Tech Ingredients made a video about hydrogen's and sf6's sound dampening abilities.

I pretty much switched to Firefox when Edge switched over to Chromium 'cause I'm a bit scared of a Chromium monopoly...

Recording music has been part of my career as a musician and I've learned about a speaker being wired up as a microphone in order to enhance certain frequencies. I haven't tried it yet but it just seems like a really cool idea. Great video man!

I noticed something similar happening with my desk's studio monitors. They redirect quiet sounds from around the room (e.g. air filter, snoring cat, etc.) and focus them to specific points depending on their relative angle to to the monitors' woofers. Very cool!

No views and no comments, this gotta be the earliest I've ever been to a video!

"The intuitive one that I like involves looking at the wavefront. It's important to know that light travels more slowly in a medium with a high refractive index. So, look, as the light goes from air to glass, it slows down, and so the peaks and the troughs of the wave need to bunch up a little bit. In other words, the wavelength shortens. If the light comes in at an angle, then this slowing down of light actually changes the angle of the wavefront. And, if we assume that light always travels perpendicular to the wavefront, then the direction of travel must change as well. The opposite is true when you go from a high refractive index to a low refractive index medium. In other words, the light bends away from perpendicular - away from normal." There are a variety of reasons why such an explanation is wholly inadequate (and wrong). The reason "the peaks and the troughs of the wave [...] bunch up" is what effectively results in slowing down the speed of light through any medium, not the other way around - i.e., the peaks and the troughs of the wave are not forced to "bunch up" as a result of light slowing down. Not only does such an explanation do nothing to explain why light slows down through a medium, it has the effective chain of causality entirely reversed. Likewise, the mere act of the light slowing down alone would not provide any grounds upon which one would observe, regardless of the angle of incidence, any change in the direction of travel of the wavefront. The wavefront would appear no different, in it's linear direction of travel, than if the wavefront were traveling perpendicular / normal to the surface. At the surface boundary interface, although the lines may become slanted and change their spacing as they change their speed, they would still be oriented in the exact same direction of travel. The change in direction of travel can not be ascribed to a change in speed alone. So, clearly, planting the root cause of refraction as arising from the slowing down of light alone doesn't approach any semblance of an adequate explanation. It's the interaction between the electromagnetic wave's own electric field and that of the electric fields induced in the material by the electromagnetic wave's oscillating electric field as it travels through the medium that results in all of the observed behaviors - i.e., the slowing down of light in any medium (other than a vacuum, obviously, due to it's inherent lack of any medium) and the refraction of light at the surface boundary interface. As an electromagnetic wave - in this case, the light - travels through a medium, the electric field of the electromagnetic wave induces an electric field (the idea of an induced field interplay can be demonstrated by a magnet slug free-falling down a copper pipe) in the material that combine to form a new resultant wave characterized by a slower speed - hence, the slowing down of light in any medium. Upon exiting the medium, only the initial wave exists, resulting in the resumption of the initial speed. Likewise, the perpendicular component of the magnetic wave's electric field, normal to the surface boundary, is opposed by the induced electric field in the material, thereby reducing the perpendicular component of the resultant electric field as it travels through the medium, which yields a change in the angle of direction - i.e., if the parallel component remains the same and the perpendicular component is reduced, the resultant vector will necessarily change direction. Upon exiting the medium, the induced field no longer exists, thereby resulting in the resumption of the original direction of travel.

This is the best explanation of how optical lenses work that I've every seen/heard

I wonder if I could get a live mix kind of sound with this... Ill pocket this into the deep recesses of my brain

Lol this is how i got the copper into the balloon. *plays video of him ripping apart balloon with copper pipe already in it... In ReVeRseE*

Nobody: Steve: *This surface here is a section of a sphere* Me: Ooh nice rhymes

Wow. I use Brave for most than a year by now. That's a good product advertising you did. Great video as always!

WOW! one picture and one sentence, I fininally understand why light was bend in materials. It is so fun to watch your video, thank you for making them!

... as usual, a great topic for presentation. Thanks Steve!

The RU-vid channel Tech Ingredients goes pretty in depth with what's happening here in his video titled "Helium vs Noise." It's interesting how the kinetic energy and the different masses of air molecules as the sound wave travels through is lensed just like lightwaves.

One thing that I remember being fascinated by in uni was learning about the existence of phonons -- much like how photons are "particles" of light, phonons are "particles" of sound! Or heat, depending on how you look at it. Regardless, it was really quite interesting to see something relating light and sound together again like that!

This is really cool! I want to see you focus ripples across the surface of liquids!

I agree, I switched to the Dissenter browser months ago and it was extremely simple. it just pulls everything from your default browser when installing.

This is the first time I've ever used an affiliate link for something advertised in the video. I'm loving the new browser, it's much better on RAM than Chrome. Even shared your link on my Facebook.

I love videos that point out something fairly intuitive that I've just never thought of before. Its like, "oh! Of course that works!" Its neat

Very cool! Thanks Steve.

During a physics class, I had trouble wrapping my head around optics. In particular, I simply could not form any intuitions about lenses. I really wish this video had come out like two months ago, so I could have them explained to me in that signature Mouldy style. Even if it's a bit late for me, I appreciate the video.

There are SO MANY things I learned and love from this video!! 👍👍👍

Back in the '70s JBL made some brilliant lenses for their midrange horns. The idea wasn't to focus the sound like you'd use an optical lens to fry ants. These lenses were designed to make an efficient horn behave like a point source so the radiation pattern was more like the other drivers. Because these were mechanical devices you could see what was going on. The sound coming from the middle was allowed to pass through mostly unobstructed, while the sound from the edges was delayed by slanted or corrugated metal plates. The resultant wavefront was similar to what a dome driver would make. And because it was purely physical, you could see how it worked.

A really snazzy demo and now we have a new riddle: "When does a concave lens focus?" How about 3D printing a concave lens that could be evacuated? Presumably you'd need to use something strong like one of Shapeways carbon materials for example and also have some internal struts which hopefully wouldn't affect the acoustics too much.

I am very very surprised that this isn't used in recording studios. You could improve isolation of different sound sources from each other if recording in the same room, like a live session or something, just using large balloons and helium. Very interesting idea.

This would make a great lab for my physics class! Thank you for the inspiration.

I haven't been willing to move away from Firefox for a long time. I never went to Chrome for privacy reasons, and I appreciate these new privacy-focused browsers coming along!

Using a non-leaking balloon to focus the sound of a leaking balloon (white noise). This is one of the only times I’ve heard someone correctly point out “irony”, rather than “situational irony”. Love the experiment and information!

I mean it makes sense, but I would have never thought of building an acoustic lens. Very nice video!

This just made me idealize an entire new lecture. Thank you. Youll be referenced

Steve thank you for this. Id never thought of audio lensing before but i know my boys will be as fasinated by this as i am. And we will try doing this as well! Stay safe with this Covid fun!

Awesome explanation! It made learning a new phenomenon very interesting for me.

You're one of the only publishers that I actually send my Brave Rewards to. I tell lots of people that I subscribe to that they should register with Brave even if they don't use the browser, but none of them ever do - even the people that reply to my comment to say thanks don't do it. I even tell them that I've tipped them so they know there is free money there for them to collect, and nobody ever picks up the tips - So I'm going to send you 10 BAT now, partly because I love your videos, but mostly because you're not a loser that refuses to embrace change like the rest of my subscriptions!

Fascinating stuff, mate.

Nice. Again. Thanks Steve!

Brave exploding onto the scene! I've been using it for 6 months and I love it. Getting rewards for browsing privately is great!

I used to work with very large non elastic balloons for film lighting, and they had large caps on the ends which were open when deflating. If you put your arm inside and snapped, it was super muffled from how the helium attenuated the sound. It was actually kinda unpleasant to be very close to one when it was inflated, but I think that was more a result of the change in the speed of the sound reaching one ear over the other

A nice research.Thank you for the idea

Another place where acoustic "optics" and normal optics meet: At the observatory I volunteer at, volunteers sometimes worry about the sound of loud running water in the dome! When the dome slit is open towards the fountain in the lake next to the observatory, from some parts of the dome you can hear the water as if you were right there. Similarly, sounds from inside the dome can often be heard by those outside. The shape of the dome is a paraboloid. There is, of course, a telescope inside. Like the dome reflecting sound, the telescope uses mirrors to reflect light.

very cool, i have seen, or heard, this effect from sitting across from someone else with a ripping hot bon fire between us on a cold night. It makes sense why i only remember it on cold nights as opposed to hot summer ones due to the greater change in air densities.