# this is kind of a video about filters ## Метаданные - **Канал:** Angela Collier - **YouTube:** https://www.youtube.com/watch?v=Z-F3JEpGFa4 ## Содержание ### [0:00](https://www.youtube.com/watch?v=Z-F3JEpGFa4) Segment 1 (00:00 - 05:00) I spend a lot of time on this channel calling out billionaires for their stupidity and I do earnestly and honestly think that is very important. I think it's important to look at these people and say, "Hey, that sounds dumb. Those are the words of a stupid person. Perhaps maybe it would be a better idea to not give them unilateral control of our government and our personal data and you know the fate of the planet because they sound stupid. I think it's important to say that. But of course evil billionaires are not the only people that can behave stupidly. Like regular normal everyday people can do evil stupid [ __ ] Like those people who drive drunk monsters or you know those people who don't vaccinate your kids. You deserve nothing but shame and mockery and derision like bad. You are a bad person. But most people are just chill, right? And chill people also do stupid things. But those stupid things don't cause harm to others. And when you do something stupid that doesn't hurt anybody and you didn't mean anything and like it was a mistake you learned from, I think that that's fine. Funny even. And who would I be if I sat here and pretended that I never did anything or said anything stupid? That just simply would not be true. And so I thought, you know, for Christmas, there's no way this is coming out by Christmas. Um for the Christmas season, you know, why not a story where I'm the idiot for once, where I'm the dumb dumb. That'll be fun. Uh this video is about filters, by the way. So, if you're just here for the filters, for baby's first filter, skip to this time step, but it is in fact going to be baby's first filter. So, like if you already know a lot about filters, it's fine. You're probably not that interested in it. So, here's the story. Around Thanksgiving, I carved out some time to film a video. This is the video. It's on my main channel. It's still up right now. I figured this video would take me about three hours to film. So, I allotted three hours in a day and I sat down to do it and I got about halfway through when I got a text message. I think you can even hear my phone like buzz in this video. You can hear me get the text message. And the text message was just like, "Hey, you actually don't have three hours. You have about 30 minutes left. " And I made the stupid decision, one of many in this video where I was like, "Okay, I will just rush through the rest of the video. like I'm already halfway done. I have 30 minutes. Like this will be fine. I'll just rush through. And that's just dumb cuz when you rush through, it's never good. I don't write scripts for these videos. Like I'm not staring at a teleprompter right now. Th This isn't scripted. I write a little outline and kind of the beats I want to hit and then I just say words for like three hours and cut it down to like an hour usually. It would be funny though if I did have like a crew and a teleprompter. And right now at this very moment like this the video guy like turned the screen on a teleprompter and I'm just reading the words. I don't have a telepromp that would be funny but it's true. So it's not funny I guess. [snorts] So you can tell it's not scripted. I rush through it and days later I sit down to edit. I edit the first half. It's fine. I get to the second half that I rush through and it's bad. It's real bad. I'm just saying nonsense and none of it's cohesive and because I'm rushing like my whole like throat is like cracking and it's bad and I knew that was going to happen. I was so annoyed, but I knew it was going to happen. So, I just I had to film it again. the second half again. And this time though, I forgot to turn off the heater. And I always turn off the heater because I'm trying to make my videos sound better. and the heater I feel like can be distracting. So I recorded the video, the second half of the video again and it was fine this time and when I go to edit it I just hear like that [snorts] and I was like no there is a constant identical frequency hum a constant bit of noise in my video. Oh no, I think I'm going to have to film it again. And this is where the stupid part starts. This is where I am a dum dum. I am a dumb person. I actually would love it. I think it would be really funny if you left a comment with the timestamp of where you realize what the the action I need to take is where you realize my mistake and just comment it and then I could collect the data and make a little curve because I feel like if you've ever edited like a single video in your life, you know exactly what I should have done at this very ### [5:00](https://www.youtube.com/watch?v=Z-F3JEpGFa4&t=300s) Segment 2 (05:00 - 10:00) second. If the problem is that my video has a very consistent low frequency hum inside of it, what could I do about that? H [snorts] well, let's all come to the solution together. We'll see how long it takes you. So, I of course think I have to record it again. That's the easiest thing to do. Just record it again. But like it takes it doesn't take me a long time to record. It's just like I have like a job and everything. I have to like set a specific time and it's usually at night and I come down to my little basement and I turn off the heater and I record the videos. So like if I mess up like that, it's like three more weeks until the video comes out. And I'm sitting there thinking, well, the first half is fine. And most people turn it off after 30 seconds anyway. Only the real ones are still watching after 30 seconds. And also, I can hear you saying, Angela, do you really care that much about a video where you just make fun of billionaires for being afraid of death, but also refusing to live? And like, I do think it's important. Yeah, I'm sorry. That's embarrassing. It's true. I think it's important to make videos like that. That's why I do it. But I then I think I use my brain. I think, Angela, you have paid and purchased professional video editing software that you have a license to. You could just pull the MP4 into that, take the MP3 off, save it as a file, and you could just edit that audio file. You could put a filter on it. You know how to do that. You do that all the time. You're a professional physicist. All you do is analyze data. You could look at a signal and process it and remove a low frequency hum. That would be so simple. That's what you should do. So again, I go to the video editing software, which I have fully purchased and paid for. I open the video editing software, the professional video editing software I own, and I take the MP3 and I save it to my desktop and I open up Notepad++. You see, I usually edit in Vim. But for some reason, if I'm like starting a new script or a new document, it feels weird to me. So I always open Notepad++ and make a document and like copy and paste my little import mattplot lib into that and I start the process there and then any other time I edit it, I edit it in Vim. That's kind of weird. That doesn't make any sense, but it just that feels right. So I'm in Notepad++ and I learn how to load an MP3 into Python and I'm like cool. Now I have a list of numbers. I can do this all day. I know how to process data. And um that's like a hubris. you have this combo of stupidity and hubris where I'm like I can edit data. I don't I've never worked with sound files, but I'm sure it's the same. And there's actually like a lot that goes into the weeds of like sound editing, but I assumed that file would be some sort of waveform, something like this, and I could take the Forier transform of that and I would get a power spectrum of frequencies. And the higher frequencies would probably be me just like yip yapping. And somewhere in those lower frequencies would be the air conditioner. And I could just make a cut, make a filter and be like, if it's a low frequency, just don't put it back in the file. Just cut all of that from the file. And then when I took the MP3, I could put it back into my professional video editing software that I've already paid for and purchased with my own money and it you wouldn't be able to hear the air conditioner. I was like, I could just do that. But then, really proud of myself here, I had a big brain energy moment. I thought, baby girl Angela, you already have professional video editing software. You don't need to be searching through this list of frequencies to find what the frequency is. What you can do if you were smart, Angela, is go back to the editing software that you've already purchased and paid for and find like a 15-second snippet where you you're not talking and it's just the air conditioner, like when you're like reading your notes or something. And when you look at the fa transform of that time step, you will find the largest amplitude, the highest power frequency is that of the air conditioner. And then you will know exactly where to place your filter. Duh. So I close Notepad++ because now I will of course edit the file in Vim. The file already exists. You don't need Notepad++ anymore. That's so weird that I do that. I didn't notice I did that till I was writing down this process. And I find my 15-second timestamp and I'm like, perfect. I don't have to film this video again. I am saving so much time by writing a Python script to remove the noise of the air conditioner. So, I write down my little 15 second time ### [10:00](https://www.youtube.com/watch?v=Z-F3JEpGFa4&t=600s) Segment 3 (10:00 - 15:00) stamp on a post-it. I minimize my video editing software that again is a professional I fully paid for. and like have access to all of the components and buttons. And it was in that moment when I clicked minimize on my professional video editing software that I've already paid for that I was like, "Oh my god, this already exists in this software. This is just a thing you can do. " Of course it is. You dumbass. You fool. You absolute dummy dumb dumb. Of course you can filter noise in the professional video editing software. Like that's got to be like someone invented recording sound. The second thing they did was invent a way to filter that sound and get rid of noise. Like the reason video editing software exists is probably like number four on that list to remove background noise. Of course, it already exists in the software. Any video editing software in the year 2025 would have a noise reduction algorithm in it somewhere. I am the dumbest person in the world. This is of course the solution to my problem. again. Let me know anywhere in this process where you would have figured it out because I am so embarrassed about when I figured it out. I jump onto Google and I type video editing software. Listen, if you want me to say what video editing software I use, perhaps they should pay me advertising how easy and fast this process was for free in this economy. I don't think so. But also, every single video editing software that exists right now, even the free ones, even the ones that are like browserbased would do this because it's such an obvious thing that they would do. I Google the video editing software I have, plus air conditioner noise, plus Reddit, and it takes me to a thread, and the thread was like, drag and drop this, and then check the box that says hum reduction. So, I did that and it took like once I found the correct button, it took like less than a second to fully render and I listened to it and you couldn't tell. And I posted that video and no one said a word about the air conditioner, so I assume no one else could tell. [snorts] If I had known what button to click, it seriously would have taken me less than 1 second. I went from, "Oh no, I have to re-record this video. It's going to take so much time to haha I'm smart. I can reduce data. I know how to process large arrays of N. I can do that. I can do a 4A transform. So like oh my god of course this exists. I can just push a button. Wow. Everybody makes mistakes and everybody has those days. And I think it's funny. I think it's fun. I think that's a funny story where I'm an idiot. I'm the dumb dumb. I was a real piece of [ __ ] that day. Anyway, the idea I had, the thing I started writing in Python would be a digital filter. And I think that totally would have worked. It just would have taken me a lot more time. It like messing with it. And then also what I was most worried about is also a thing I don't know a lot about, but it's like the frame rates. Like if I record a video on a camera and I record the audio on a different device, like they have different internal clocks and so a lot of times the sound and the video will be off by like a few frames and then if you're 2 hours into a video, it's like noticeably off. So what worried me was if I took the audio file and then processed it in a different resolution and then shoved it back onto the video file, it would take a whole lot of fiddling to match everything back up. And I thought that would be more annoying for people than the air conditioner sound, but I was going to try it. It would have taken me hours. But of course, it would have saved more time than refilming the video. But then, of course, I learned about the magic little check box that has the algorithm because of course people have been doing audio processing since the invention of the radio. Angela. [sighs and gasps] Anyway, that's what a digital filter is. You take some sort of analog data. In this case, it would be my voice and you convert it into a digital signal and then you do whatever you want with it. Like in my case, I was just gonna slap a loop on it and be like, if the frequency is lower than this, cut it. Make it a zero. You know, but that that's still a processing technique. Of course, what would be in software now would be much more advanced and sophisticated, and there would be some sort of mathematical function that ### [15:00](https://www.youtube.com/watch?v=Z-F3JEpGFa4&t=900s) Segment 4 (15:00 - 20:00) would probably smooth the signal in a much fancier and less obvious way. But I still think my technique would have worked. And I'm pretty sure what I'm describing would be a highpass filter because my yip yapping is at a higher frequency and air conditioner HVAC noises, which is going right now. Can you hear it? Did I remember to fix this audio would be a lower frequency. So, I would create a filter that only allowed highpass frequencies like my voice to pass through and it would have made the sound more pleasant. Well, I mean, you'd still have to be listening to this. I say I'm pretty sure that's a highpass filter because it changes depending on what field you're in. And I feel like some sort of optical engineer would be like, is that a highp pass filter? Would you call it that? And I'm not sure about your field, but the way I'm describing it is like low frequencies are blocks. High frequencies can pass through. That's what I would call a highp pass filter. Your mileage may vary on that. But anyway, you take the processed signal and you shove it through a DAC or something and it can convert it back into an analog signal. And what you get is the same signal, the same analog signal you originally recorded, but just processed, maybe smoothed, maybe with noise reduction, that kind of thing. And doing this digitally is multiuse. And oh my god, of course, professional video editing software already has these things built in. Of course, I just I would never think to do it because I am not a professional video editor. I would never think like, "Oh, of course people do this all the time. This must be in here. " What I thought was, "Oh, of course I specifically do this all the time. I can just do it the same way I always do it. Write a Python code. " It's just it's my solution to this problem is stupid, but also very funny. like I chose the laziest way to go about it, which is the way I always do it, but also it was the dumbest possible way to go about it because there's a much easier way. Also, I do realize at this moment in 2025 when you talk about filters, people might be imagining like Photoshop filters, like those filters, your iPhone will just like appear onto your camera and you take like eight pictures before you're like, "What the [ __ ] is wrong with my face? " And you have to go find the settings to turn that off. Those types of filters are identical to the digital filters I just described, except instead of smoothing or reducing the noise in sound, they do it on images. It's the same process. It's the same like take analog data, turn it into digital data, do some fancy math on it. Same thing. But what I think is much cooler is analog filters. So digital filters are all software, but they of course replace a thing that used to be analog. And there are still analog filters, of course. Um, I just think it's much more intuitive and much more interesting to look at analog filters. What I always think about is radios because modern radios are all modern software and integrated circuits and stuff. I'm thinking like pre-transistor radios. Amateur radio building was this huge thing. And I would argue like ham radio, which is the grandchild, is still a huge thing with amateur electronics people. Um, but in like the 1910s, people would buy these hobby kits and they would build these little radios and it just kind of got huge. Like they started with these crystal radios and then by the 20s and 30s you had like the vacuum tubes and people would build their own radios. They would open up their radio and look at the circuit and know how it functioned worked and they could replace components of it. old physicist, physicists who grew up in like the 30s and 40s, they would always say the thing that made them a physicist was looking inside a radio because you could see the circuit. You could see how the circuit related to how the electricity moved through the circuit. You could see how these physical components commanded electricity and magnetism. And it was a real like physical realization of these physics concepts that they would use as they became professional physicists. And we were robbed. We will never see that again because everything's so teen tiny and printed and you can't the old radios, they don't exist like that anymore. Which is why today if you were to take a modern elementary physics class, people would still talk about old-timey radios and they would draw the little circuits just like they would appear in an old times radio because that way of visualizing it is really helpful when you move on to the more complicated and more abstract even like circuit design things. Anyway, as I am forever regretting my decision to become a theorist instead of an experimentalist, I thought a fun way to end this video would be to assemble a lowass filter. And I've already done it. I did that part first. I thought it was ### [20:00](https://www.youtube.com/watch?v=Z-F3JEpGFa4&t=1200s) Segment 5 (20:00 - 25:00) interesting. I built a little lowass filter. So, here's how I set it up. This circuit will allow low frequency signals to pass while blocking higher frequency signals. So at low frequencies, the capacitor acts as an open circuit. So the input signal kind of just flows straight through to your output and you measure exactly what you put in. But at high frequencies, the decreasing impedance diverts the signal and the capacitor kind of acts like a short. So you don't measure anything. So when frequency is infinity, you would measure zero. When frequency is trending towards zero, you would measure the exact voltage that came out. If that makes sense. I will put the circuit diagram, right? diagram right here. But as you can see, I have a resistor and a capacitor right here. And I have a function generator here that is sweeping through frequencies, giving this thing a range of voltages. And this, as I have set it up, is a lowass circuit, which means that low frequencies should pass right through and high frequencies should be cut off uh on a diagram that looks like this right here. And to test this, I just I hooked up one of my many oscilloscopes. And uh what we're looking at is that result. Uh let's see. What you're looking at here is me measuring the voltages at two points. You can see there's a yellow actually I don't know what color it's going to show up for you. There's a yellow background and a green curve. The yellow background I have placed the probes ahead of the capacitor. So this is just measuring the voltages that come straight out of my function generator that they will be different frequencies but the amplitude will be the same for all the frequencies. You can see this flat curve because it's not going through my filter. And then I have probes at the filter. And you can see that for lower frequencies, I'm measuring those same high amplitudes. But as you increase the frequency, I have filtered out those voltages. I am not measuring a high amplitude for those voltages. I'm really happy with this as like a proof of concept. Of course, you could look at my circuit and you could say this is the capacitance of the capacitor and this is the resistance of the resistor and here are the frequencies that I'm sending through this circuit. And then you could calculate like what the amplitude here is. You could calculate what the slope of this curve is for the drop off and that would change if you were to swap out the resistors or the capacitors. For example, I actually have a second capacitor here which will change the overall capacitance of the circuit. And if you look at this curve here, like how thin this is, how accurately the filter is blocking the higher frequencies, you can see that change when I add in this second capacitor. Okay, we are looking at the standard curve for this circuit and I'm going to add in another capacitor and we will see that green line tighten meaning that additional frequencies are being filtered out. Well, not maybe additional frequencies, but the amplitude of them those frequencies is getting smaller, meaning we're reducing the noise. Um, yeah, there it goes. Ignore all of those little curves that are probably effects of me and my circuit building and the components themselves. But isn't that neat? So that the line gets shorter, meaning the filter is filtering when we add in a second capacitor and we take it off. And there you go. There's our old curve. That's really cool. As proof of concept, I think that this is really exciting. We built a little filter. Okay. So, we did it. Did you see how we did it? I visualized it on my oscilloscope. I had the little yellow line showing the input voltage at all these like high amplitudes at all these frequencies. And then the little green line was showing you the voltage after it had gone through the filter. Meaning I had successfully made a little filter. So your girl can do it in Python, she can do it on her little breadboard, and also she can Google software plus Reddit plus reduce noise on a video editing software. So like all three, I'm a triple threat filters. ### [25:00](https://www.youtube.com/watch?v=Z-F3JEpGFa4&t=1500s) Segment 6 (25:00 - 29:00) Cool. As I said, I'm a theorist and I always regret that decision because I love to build stuff with my hands. But even assembling something like that, like you can immediately see how theory just fails you, like all of those little squigglies that appear on the oscilloscope, like who's explaining that? Like the connections you have, how well your wire is plugged in, all of those things can have these huge drastic effects on what you read out. And it's not just this perfect like oh you have put the resistor and capacitor and now you have a filter you know like even the idea of a filter as like a cut off of like frequencies can go through if they're high and they get blocked here is just not a factual thing that you can create. Um when you see the plots of how these filters work you always see this kind of like drop off because some of those frequencies are getting through. You know, you can't make a perfect filter. Of course, the one I made is like really shitty and basic and like dog [ __ ] compared to like what actual electrical engineers can make with modern components and modern methods. But like you can never get theory in the lab. on the bench like that. That always gets me. Every time I try to do anything, solder or build something, I'm like, why isn't it perfect? And it's because theory is not real. So anyway, I hope you enjoyed my stupid story where I was stupid, where I was the dumb dumb. And um I think it's kind of funny. Like it's funny because I I don't think like a video editor. So it just wouldn't occur to me to be like, "Surely there's a surely there's a little algorithm in here that'll reduce the noise for me. " Of course there is, Angela. Duh. You fool. You clown. my brain just immediately goes to data and I'm like I can process data. I do that all day and it kind of led me down this rabbit hole of building a little filter which was fun. I learned a lot just like plugging my little components looking at my oscilloscope finally turning that one on. I have a bunch of vintage oscilloscopes but I wanted like a new one and so I got that one and like there's so many buttons. It's got a touch screen. I much prefer the old ones but I figured it out. It's fine. — Hey, this is editing Angela. I just wanted to say if you think this sounds like I'm being mean to myself, you should know that I don't feel that way. I think being stupid for a moment is funny and it means you learned a thing. It's like that XKCD comic. Like I would rather feel stupid sometimes because I am learning new things versus the alternative. If it hurts your feelings to call yourself stupid, just like don't do that. Follow your heart. But like if I was Sam Alman and I said the thing stopping us from having a Dyson sphere was electrons. I would really hope someone would pull me aside and go like, "Hey, dum dum. That was dumb. You're dumb. You got to stop. " You know, and I appreciate that right now at that this moment in my life, I can be that person to be like, "Wo, that was dumb. That was silly. Let's learn from this. " You know, I think that's good. But I think that that's gross. Look at this. Look at us. Look at where we are. Wow. Okay. Bye. It's a mess in here. --- *Источник: https://ekstraktznaniy.ru/video/40049*