Laser + mirror + sound

I made a video a while back about Chladni Figures which are a way to visualise the resonance of two dimensional objects, like this square plate. And ever since then, I’ve been on the lookout for other ways to visualise sound through the vibrations that they make or, the vibrations that make them. So I was really happy to come across this one thanks to Brian Mackenwells. He showed me this demonstration and he’s allowed me to steal it for my channel. So here’s the setup, I got a Bluetooth speaker, which I’ve put inside this bowl. And then, I’ve stretched a giant balloon over the top. And then I’ve glued a fragment of mirror to the surface. This fragment of mirror represents a sample of the kind of movement that’s going on on this rubber membrane, when you play music in the bowl. And we can interrogate that movement with a laser. The laser reflects off the mirror and hits my wall so any movement in the mirror will change the direction of the reflected beam. So, when we play music we see this kind of messy, chaotic pattern in the reflected beam, but if you play pure notes, you get some really interesting effects. This pure note generates a pattern that we can understand quite easily. You might imagine the membrane of the balloon kind of moving like this as the note is played which makes sense so the beam is going to be moving up and down on the wall but maybe if it’s got a bit of this motion as well then you’re going to see a kind of oval shape. What’s interesting is, as we decrease the pitch we see some changes. The first thing to notice is, as you sweep the frequency down you get these spikes in amplitude. and, I think what’s happening there is we’re hitting the resonating frequencies of the volume of air inside the bowl. As you get lower still the patterns become a bit more complicated like, you get this figure of eight, and then, you get this funny pattern here What’s really cool though, is if you start to layer different frequencies on top of each other so, this frequency creates this pattern and this frequency creates this pattern. But what about if we combine the two? And then what if we add this third frequency? So you can have loads of fun with this create all sorts of mad shapes and patterns by combining frequencies together. Here’s just a few of the patterns I’ve found by playing with two frequencies on top of each other. I wrote some JavaScript to help me sweep through the frequencies with the kind of precision that I needed If you’re interested in that code, there’s a link in the description. You’ll be pleased to know, I’ve used very few comments. This was an interesting project to film, because I came up against some of the differences between the way human eyes work and the way cameras work. So trying to recreate the live experience was a challenge like, the way we see things is continuous but the way the camers sees things is frame by frame So I’m running at 25 frames per second So every 25th of a second, you take a new frame. But you have a choice with each frame for how long to keep the shutter open for So you can keep the shutter open just briefely and then it’s closed for the rest of that 25th of a second and then you open it briefely again and then close it open it briefely and then close it or you can keep it open for the entire 25th of a second or something in between. And you often adjust that to fix motion blur or maybe you want motion blur because that’s part of the human experience, and you’re trying to recreate that. But if you set your camera to manual (sic) then it’s gonna make those calculations for you to get the right amount of light to hit the sensor. But if you’re filming something like a laser bouncing off a vibrating mirror you better set your camera to manual otherwise you’re going to have a bad time. So for example, filming with a really fast shutter speed you get this kind of pattern forming and this is nothing like the true experience of watching it live To get as close to the live experience as possible I set the shutter speed to be the full 25th of a second. But even then, there are differences, and they’re quite enlightening actually. Take a look at this freeze frame You can see the path that the laser took whilst the shutter was open and you can actually see the start and the end of the journey as well So, this is where the shutter opened the laser travels for a bit, and then this is where the shutter closed. Though actually, look a little bit closer and you can see There seems to be be more than one starting point, and more than one finishing point I don’t really know why I don’t think it’s because the laser pulses otherwise I would have noticed it watching it live, in person It may be to do with the way the frames are stored, and then reproduced. Anyway, interesting. If you have some ideas, let me know. So whilst something like this looks quite messy on camera because of all those loose ends it still looks really nice in person So, having said that, here are a few more snippets that look really nice, in person and on camera. So a big thank you to Brian Mackenwells for putting me onto that project Also a bit thank you to the sponsor for this video It’s an interesting one this time because it’s one that I use. It’s Skillshare. So, Skillshare, how do you describe it, gosh It’s like, it’s an online community I suppose for creative people, where you can work through video classes So they’ve got over 16,000 classes That you can learn about-
So cameras, for example If you’re interested in how cameras work and you want to take that knowledge and, you know, use it to make great videos and take great pictures, there’s loads of classes for you. I use the creative cinematography class, which really helped me out But whatever you’re interested in. They’ve got lifestyle stuff, they’ve got technology stuff, If you’re the sort of person who likes to improve themselves. then do youself a favour and check it out. Also, use the link in the description and the promo code because then they know that I sent you. But also, the first 300 people to use that link will get two months of premium membership free. Premium membership gets you unlimited access to all those videos. There are so many resources, so much, like, source for inspiration if you wanna try something new. And then after two months, it’s as little as $10 a month or if you don’t like it, then you can quit, and it won’t cost you anything. So there you go, check out Skillshare. That’s it really, I think Hope you enjoyed the video. If you did, don’t forget to hit Subscribe and click on the notification bell as well because my videos are a bit sporadic at the moment that’s the best way to make sure you definitely hear about new videos. Alright, I’ll see you next time.

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