WEBVTT - Rerun: Shh! How Soundproofing Works 0:00:04.240 --> 0:00:07.240 Welcome to tech Stuff, a production of I Heart Radios 0:00:07.320 --> 0:00:13.800 How Stuff Works. Hey there, and welcome to tech Stuff. 0:00:13.840 --> 0:00:16.320 I'm your host, Jonathan Strickland. I'm an executive producer with 0:00:16.360 --> 0:00:19.120 I Heart Radio and I love all things tech, and 0:00:19.320 --> 0:00:22.079 we're going to take another look at a classic tech 0:00:22.120 --> 0:00:26.120 Stuff episode of another one that published back in. This 0:00:26.160 --> 0:00:30.960 one is called how Soundproofing Works, and Noel Brown joined 0:00:31.000 --> 0:00:33.839 me for that episode to talk about the science and 0:00:33.960 --> 0:00:38.080 tech behind sound proofing, which is a very important component 0:00:38.520 --> 0:00:43.360 of our podcasting business. Here, I am currently baffled, or 0:00:43.360 --> 0:00:46.600 at least I'm surrounded by baffling, so that we can 0:00:46.640 --> 0:00:49.680 control the way that the sound bounces around inside the 0:00:49.720 --> 0:00:54.080 studio so you guys don't get terrible vocal effects. But 0:00:54.320 --> 0:00:56.080 Noel has a lot more to say about it, so 0:00:56.240 --> 0:00:59.720 let's sit back and enjoy this classic episode. So one 0:00:59.760 --> 0:01:01.200 of the things I like to do on the show 0:01:01.280 --> 0:01:03.600 is at the end of every episode, I invite you 0:01:03.640 --> 0:01:08.560 guys to send me requests ideas topics for future episodes, 0:01:09.000 --> 0:01:12.760 and today's episode is due to that. So I'm going 0:01:12.800 --> 0:01:19.920 to read a little bit of listener me. You know, 0:01:19.959 --> 0:01:22.160 we used to have a whole claxon all right here 0:01:22.160 --> 0:01:25.040 he goes, hey, you tech stuff. First off, I want 0:01:25.080 --> 0:01:27.120 to thank you for putting out your content as I'm 0:01:27.120 --> 0:01:30.280 a huge fan of this casual learning movement. Might need 0:01:30.319 --> 0:01:32.680 a better term for that. I was wondering if you'd 0:01:32.680 --> 0:01:35.440 be able to do an episode on acoustics and sound 0:01:35.520 --> 0:01:39.720 dampening for studios, like how they're measured, tuned, made, et cetera. 0:01:39.920 --> 0:01:42.360 It would be awesome and spectacular as I would be 0:01:42.440 --> 0:01:44.800 able to harness the power to put together a kick 0:01:44.840 --> 0:01:47.680 ass set up. Thanks again for what you do. Dub 0:01:47.920 --> 0:01:52.080 nosis well dubed. We're going to do that for you. 0:01:52.240 --> 0:01:54.200 And that's really the reason why I asked Noel to 0:01:54.240 --> 0:01:57.680 come in here, because Noel, as a producer and sound 0:01:57.720 --> 0:02:02.400 engineer type person, has had real world experience with this, 0:02:03.080 --> 0:02:06.240 and so we're going to rely heavily upon his um 0:02:06.440 --> 0:02:09.480 perspective some of the stories he has to tell about 0:02:09.600 --> 0:02:13.559 the process of trying to make a room more soundproof 0:02:13.720 --> 0:02:16.640 or tuning a room so that you're getting the sound 0:02:16.720 --> 0:02:19.480 you want while you're recording, because, as it turns out, 0:02:19.520 --> 0:02:23.239 sound is a pretty tricky thing. When you boil it down. 0:02:24.280 --> 0:02:28.799 Sound is vibration, right, It's just particles banging together a 0:02:28.840 --> 0:02:31.120 sentile thing you gotta wrangle. It is a thing you 0:02:31.160 --> 0:02:35.720 gotta wrangle. We often consider sound to just be this 0:02:35.960 --> 0:02:39.080 thing we perceived with our ears, But what's really happening 0:02:39.200 --> 0:02:43.440 is a little more granular than that. Sound is particles 0:02:43.480 --> 0:02:47.760 that are moving vibrating. Uh. Typically we're hearing things that 0:02:47.800 --> 0:02:51.880 are coming through over the air, like actual air around us. 0:02:52.240 --> 0:02:55.520 So you listening to this right now, you can hear 0:02:55.680 --> 0:02:59.040 my voice. Well, what's actually happening is that some speakers 0:02:59.120 --> 0:03:03.440 are vibrating some air molecules, and that is compressing and 0:03:03.520 --> 0:03:07.800 decompressing those molecules. It's it's changing the pressure, increasing and 0:03:07.800 --> 0:03:12.079 then decreasing the pressure at frequencies and amplitudes that your 0:03:12.120 --> 0:03:15.079 ears pick up and then you perceive a sound. So 0:03:16.120 --> 0:03:19.000 this is happening through all sorts of media, not just air. 0:03:19.080 --> 0:03:21.320 It can pass through solid matter, it can pass through 0:03:21.360 --> 0:03:24.120 liquid and depending on how the particles are packed and 0:03:24.400 --> 0:03:27.120 the space between them, sound may move better through one 0:03:27.200 --> 0:03:32.200 medium than through another. Now, knowing that sound can travel 0:03:32.200 --> 0:03:34.720 through different media, you also need to know that it 0:03:34.760 --> 0:03:39.440 can transfer from one medium to another medium. So for example, 0:03:39.560 --> 0:03:43.760 if I'm shouting really really loudly in a little room, 0:03:43.920 --> 0:03:46.280 some of that sound when it makes contact with the 0:03:46.280 --> 0:03:50.320 wall actually causes the wall to move. Now it's not 0:03:50.360 --> 0:03:53.160 causing the wall to move a lot, but it is 0:03:53.240 --> 0:03:55.920 making the wall vibrate a little bit. Those vibrations get 0:03:55.920 --> 0:03:59.280 transferred through the wall to the other side. And that's 0:03:59.280 --> 0:04:02.040 why if you're in a place that has, you know, 0:04:02.080 --> 0:04:05.520 flimsy walls, you can hear someone in another room. The 0:04:05.520 --> 0:04:08.000 sound is actually transferring through, not to mention in the 0:04:08.080 --> 0:04:11.760 room itself, that sound is actually reflecting back at you. 0:04:11.800 --> 0:04:14.440 And the quality of the sound can depend, you can 0:04:14.520 --> 0:04:16.800 vary greatly depending on the material that the room is 0:04:16.839 --> 0:04:19.080 built out of or treated with. Right right, So some 0:04:19.160 --> 0:04:22.440 of the sounds getting transferred through the materials, some of 0:04:22.440 --> 0:04:26.120 the sound is being bounced back from the material toward you, um. 0:04:26.400 --> 0:04:29.520 And a lot of that depends upon the the hardness 0:04:29.680 --> 0:04:31.800 of the material, Like a really hard material is going 0:04:31.839 --> 0:04:34.240 to bounce a lot more sound back at you, which 0:04:34.279 --> 0:04:36.880 is why if you are in a large room with 0:04:36.960 --> 0:04:40.159 a lot of hard surfaces you get that echoe sound. Um. 0:04:40.440 --> 0:04:43.720 Or if you're out someplace like at a canyon and 0:04:43.760 --> 0:04:45.560 you do a shout and you get that echo back, 0:04:45.600 --> 0:04:49.240 it's because the sound is going out hitting the walls 0:04:49.279 --> 0:04:52.040 of the canyon bouncing back to you, and that's when 0:04:52.080 --> 0:04:57.719 you get to experience that effect. Well. Obviously, this means 0:04:57.760 --> 0:05:02.159 that if you want to create a place where the 0:05:02.279 --> 0:05:06.640 sound can't escape or leak into and a lot of 0:05:06.680 --> 0:05:08.880 recording studios, you want both of those things right. You 0:05:08.880 --> 0:05:11.280 don't want the sound from the studio to leak outward, 0:05:11.480 --> 0:05:13.960 but you also definitely don't want outside sound to leak 0:05:14.080 --> 0:05:17.400 into the important Then you have to figure out, well, 0:05:17.440 --> 0:05:19.800 how do we limit how do we work within the 0:05:19.800 --> 0:05:24.840 physical uh uh constraints of the way sound works, so 0:05:24.880 --> 0:05:27.360 that we can limit that as much as possible and 0:05:27.480 --> 0:05:33.119 try to have the purest experience as we can. Um So, 0:05:33.720 --> 0:05:36.840 one thing you can remember is that sound, because it's 0:05:36.839 --> 0:05:40.880 a physical activity and because it relies on on energy, 0:05:41.600 --> 0:05:43.559 the way it works is that you've got a source 0:05:43.600 --> 0:05:48.720 of the sound. Sound waves travel outward concentrically outward from 0:05:48.760 --> 0:05:51.960 that source, and they get weaker as they travel out 0:05:51.960 --> 0:05:54.760 that that energy starts to dissipate. You can think of 0:05:54.760 --> 0:05:58.080 it kind of like um uh. You know, each each 0:05:58.120 --> 0:06:00.360 time a particle has to bang up against the another 0:06:00.400 --> 0:06:02.719 one to move it, some of that energy ends up 0:06:02.760 --> 0:06:05.000 getting lost. So the further way you are from a 0:06:05.040 --> 0:06:07.560 source of sound, the quieter it is. That's why that happens. 0:06:08.120 --> 0:06:11.520 So one way you can limit the way sound comes 0:06:11.520 --> 0:06:14.160 out of a room is you make an enormous room, 0:06:14.440 --> 0:06:18.800 like you have a little room in a really big room. Um, 0:06:18.839 --> 0:06:21.960 But that's not necessarily the most practical approach. Actually, there's 0:06:21.960 --> 0:06:24.520 a studio I used to intern at in Athens, Georgia 0:06:24.520 --> 0:06:28.520 called Chase Park Transduction, and they essentially built their studio 0:06:28.800 --> 0:06:32.279 inside of a larger warehouse space. So they're renting a 0:06:32.320 --> 0:06:35.000 space in the strip of big, giant, very high ceiling 0:06:35.000 --> 0:06:38.279 warehouse spaces. But when you go into the studio, you're 0:06:38.400 --> 0:06:42.920 in the warehouse. But then there's a smaller basically building 0:06:43.440 --> 0:06:46.640 inside that warehouse that is the one that receives all 0:06:46.680 --> 0:06:49.280 the acoustic treatments. But it's like you said, I mean 0:06:49.360 --> 0:06:52.160 that is one way of dealing with it is air. Yeah, 0:06:52.360 --> 0:06:55.520 the room within a room approach is often how it's 0:06:55.560 --> 0:06:58.880 referred to, and sometimes it is not as obvious as that, 0:06:58.920 --> 0:07:01.160 Like it may be that uh, it looks like the 0:07:01.520 --> 0:07:04.680 the room you're walking into might be like it's it's 0:07:04.800 --> 0:07:08.080 in a little uh alcove or hallway, but that hallway 0:07:08.160 --> 0:07:11.200 is actually showing where the the walls are, where there's 0:07:11.200 --> 0:07:14.480 an air gap between the two walls to to mitigate 0:07:14.520 --> 0:07:17.880 any sound coming into the space. Here. Even this glass 0:07:17.920 --> 0:07:19.920 window that we have in the booth that we're recording 0:07:19.960 --> 0:07:22.640 in right now, it's a double paned window. So in 0:07:22.720 --> 0:07:25.760 between these two relatively thick pieces of glass is a 0:07:25.800 --> 0:07:28.400 little layer of air, which in and of itself acts 0:07:28.440 --> 0:07:32.880 as a bit of a sound dampening insulation device, right exactly. So, uh, 0:07:33.040 --> 0:07:35.400 some other little elements of sound that we need to remember. 0:07:36.120 --> 0:07:40.360 There are two main components to a sound wave that 0:07:40.440 --> 0:07:43.560 are important to keep in mind. One is amplitude or volume. 0:07:44.000 --> 0:07:47.600 So if you are looking at the way we typically 0:07:47.720 --> 0:07:49.600 show a sound wave which is on like an X 0:07:49.720 --> 0:07:52.960 versus Y graph um, you know those those sine wave 0:07:53.040 --> 0:07:57.120 style graphs, the height and depth of the troughs that 0:07:57.160 --> 0:08:00.960 represents the amplitude how loud the sound is. Then you 0:08:00.960 --> 0:08:04.200 have the frequency of sound, the number of times sound 0:08:04.520 --> 0:08:08.920 cycles within a second that determines the pitch of a sound. 0:08:09.080 --> 0:08:13.120 So a low frequency obviously would be a perceived as 0:08:13.160 --> 0:08:16.560 a lower deeper note or tone, and a high frequency 0:08:16.640 --> 0:08:20.320 with those peaks and troughs moving gradually more closer together 0:08:20.440 --> 0:08:23.920 is going to be perceived as a higher pitch. A 0:08:23.960 --> 0:08:25.720 good way to think about this too, is if anyone's 0:08:25.720 --> 0:08:28.760 familiar with the instrument the theoremin. There are two controls 0:08:28.760 --> 0:08:31.240 on a theoreman. One is the antenna that goes upward, 0:08:31.280 --> 0:08:33.480 and there's an antenna on the side. Uh. The antenna 0:08:33.520 --> 0:08:35.640 on the side you use your hand by moving it 0:08:35.720 --> 0:08:39.280 closer to or farther away, you are changing the amplitude, 0:08:39.440 --> 0:08:42.280 and that's perceived as a change in volume. The antenna 0:08:42.320 --> 0:08:44.440 going up as you move your hand closer to it 0:08:44.520 --> 0:08:47.360 or farther away, you are changing the frequency. So with 0:08:47.400 --> 0:08:50.880 those two controls you can basically shape the way the 0:08:50.920 --> 0:08:54.280 sound is perceived. Right, And it's important to remember these 0:08:54.320 --> 0:08:58.280 things because uh, As it turns out different approaches to 0:08:58.400 --> 0:09:03.080 sound proofing are effective for different frequencies. Definitely, right. So 0:09:03.120 --> 0:09:05.520 there might be one that you're like, oh, this is 0:09:05.679 --> 0:09:08.840 this is perfect, I can't hear my neighbors anymore. But 0:09:08.920 --> 0:09:11.280 then it turns out that when your neighbors put on 0:09:11.559 --> 0:09:13.439 a an album that has a lot of base in it, 0:09:13.440 --> 0:09:16.079 it comes right through or start yelling at each other 0:09:16.120 --> 0:09:19.040 for whatever. Yeah, the amplitude is loud enough, it maybe 0:09:19.040 --> 0:09:22.839 that you're soundproofing isn't going to be uh. When people yell, 0:09:22.880 --> 0:09:25.079 sometimes they tend to raise the pitch right right right, 0:09:25.120 --> 0:09:27.520 the pitch goes up enough, but I got you. Yeah. 0:09:27.600 --> 0:09:29.760 So these are things that you have taken to consideration 0:09:29.800 --> 0:09:32.680 if you're trying to sound proof, and obviously what you 0:09:32.760 --> 0:09:36.000 are trying to accomplish, like the reason why you're soundproofing, 0:09:36.400 --> 0:09:38.040 that will play into it as well, because if all 0:09:38.080 --> 0:09:40.360 you're trying to do is just make it quieter so 0:09:40.400 --> 0:09:43.080 that you know, you don't have like you're designing a building, 0:09:43.320 --> 0:09:45.720 maybe it's a hotel, and you want to make sure 0:09:45.800 --> 0:09:48.880 that the the people talking in one room doesn't bleed 0:09:48.960 --> 0:09:52.480 over into other rooms. That's one type of soundproofing. If 0:09:52.480 --> 0:09:56.360 you're trying to make a professional recording studio, that's another type. 0:09:56.600 --> 0:10:00.480 From a construction standpoint, like the base level soundproofing is dryewall, 0:10:00.720 --> 0:10:03.439 So you have drywall, and that is where if you're 0:10:03.440 --> 0:10:05.600 in a hotel that only uses drywall, people are gonna 0:10:05.600 --> 0:10:07.480 be able to hear every single thing that's going on 0:10:07.559 --> 0:10:10.520 next door. It's when you start basically stuffing that dry 0:10:10.559 --> 0:10:14.160 wall with other denser materials or you know highly rated 0:10:14.200 --> 0:10:17.240 soundproofing materials. That's when you can really cut down on 0:10:17.280 --> 0:10:20.200 that transfer between the rooms, right, And also there are 0:10:20.240 --> 0:10:23.880 other some other techniques you could use as well that 0:10:23.920 --> 0:10:27.240 I'll get into that. And it's all about how do 0:10:27.280 --> 0:10:29.360 you make it harder for the sound to travel from 0:10:29.360 --> 0:10:31.520 one place to another because sound is going to travel 0:10:31.559 --> 0:10:34.200 no matter what. It's not like we have created a 0:10:34.320 --> 0:10:39.520 material that just sucks up sound totally. We've got a 0:10:39.559 --> 0:10:42.560 lot of materials that resist vibration and that means that 0:10:42.600 --> 0:10:46.240 they don't transfer sound very well. But in fact the 0:10:46.280 --> 0:10:49.400 studio has some of that around us. But you know, 0:10:49.400 --> 0:10:52.920 there's other stuff you have to take into consideration as well. Now, 0:10:53.440 --> 0:10:56.719 there are four general elements to soundproofing and we've we've 0:10:56.800 --> 0:10:59.520 kind of touched on a few of them, but one 0:10:59.520 --> 0:11:03.959 of the big ones is called decoupling. Now, decoupling is 0:11:04.000 --> 0:11:07.840 a construction term. When you're talking about decoupling, you're talking 0:11:07.880 --> 0:11:11.920 about the way the walls of the soundproofed area are 0:11:11.960 --> 0:11:14.920 actually constructed. So you were just talking about dry wall. 0:11:15.160 --> 0:11:18.200 The typical way a wall is constructed is you've got 0:11:18.280 --> 0:11:22.000 studs and attached to the studs are the anchor points 0:11:22.000 --> 0:11:26.800 for the dry wall. And in a typical wall, the 0:11:26.920 --> 0:11:30.960 studs are connected on either side by drywall for one 0:11:31.000 --> 0:11:32.280 side of the wall and dry wall for the other 0:11:32.280 --> 0:11:35.040 side the wall, So the h if you can think 0:11:35.080 --> 0:11:37.800 of it like the interior wall versus the exterior wall 0:11:37.880 --> 0:11:40.959 of a room. The problem with that is that when 0:11:41.000 --> 0:11:44.280 sound hits the drywall, then sound can travel through the 0:11:44.360 --> 0:11:48.280 dry wall through the studs, which transmit sound. They're pretty 0:11:48.280 --> 0:11:50.559 good conductor for sound to the other side of the 0:11:50.640 --> 0:11:53.320 dry wall, and then you get sound bleeding out or 0:11:53.360 --> 0:11:57.160 you have sound bleeding in from the outside. So decoupling 0:11:57.559 --> 0:12:00.240 is a process where you would build a wall so 0:12:00.360 --> 0:12:04.880 that the studs don't touch both sides of the wall. 0:12:05.760 --> 0:12:08.120 You would have a series of studs that one side 0:12:08.160 --> 0:12:11.240 the interior wall are attached to, and a different series 0:12:11.280 --> 0:12:14.040 of studs that the exterior wall are attached to. They 0:12:14.120 --> 0:12:18.679 both extend well into the gap between the two walls, 0:12:18.800 --> 0:12:21.480 but they don't touch the other side. So one side 0:12:21.480 --> 0:12:25.760 could be receiving sound waves and potentially transfer those, but 0:12:25.840 --> 0:12:28.560 since they're not touching, it's much more difficult for that 0:12:28.600 --> 0:12:30.640 to happen. Right, because air is not as good a 0:12:30.640 --> 0:12:33.920 conductor of sound as a solid object is, which is weird. 0:12:33.960 --> 0:12:35.840 You wouldn't think that, because I mean, here we are 0:12:35.840 --> 0:12:38.199 in a room talking to each other, and the air 0:12:38.320 --> 0:12:41.840 is basically what's connecting us. But the interesting thing, though, 0:12:41.880 --> 0:12:43.640 is that the way you can tell this, it's very 0:12:43.640 --> 0:12:46.720 easy way to tell. It's the old kid game of 0:12:46.720 --> 0:12:49.160 a telephone where you get two cans in a string, right, 0:12:49.720 --> 0:12:52.319 you you punch holes in the bottom of the cans, 0:12:52.360 --> 0:12:55.400 You run the string through the holes, you stretch it taut, 0:12:55.760 --> 0:12:58.079 and then you can whisper into one can and here 0:12:58.120 --> 0:13:00.120 it on the other side. But if you whisper that 0:13:00.240 --> 0:13:04.480 same volume across the room, you can't hear it. So again, 0:13:04.520 --> 0:13:08.520 that shows that the the physical media is actually more 0:13:08.600 --> 0:13:11.440 or medium i should say, is actually more efficient at 0:13:11.440 --> 0:13:15.559 transferring the sound than than air is. So air pockets 0:13:15.559 --> 0:13:19.480 are actually really important when you're soundproofing, you know, designing 0:13:19.480 --> 0:13:24.120 a soundproof room. Um, typically you would pair decoupling with 0:13:24.440 --> 0:13:26.880 some of the other elements, and I'll go ahead and 0:13:26.880 --> 0:13:28.720 mention what those elements are, and then we'll talk more 0:13:28.760 --> 0:13:31.760 about how you would put it all together. So you've 0:13:31.800 --> 0:13:37.160 got absorption another important element. This is obviously using a 0:13:37.240 --> 0:13:41.559 material that slows down sound. Uh, it absorbs some of 0:13:41.600 --> 0:13:44.480 the sounds, so that sound essentially loses some of its 0:13:44.559 --> 0:13:48.439 energy and it thus is quieter. It doesn't it doesn't 0:13:48.480 --> 0:13:51.240 leak out as much because the amplitude gets reduced as 0:13:51.240 --> 0:13:55.800 a result. UH. So absorption you achieve usually through using 0:13:55.800 --> 0:13:59.719 some sort of insulation material like UM. I mean, fiberglass 0:13:59.840 --> 0:14:02.200 is a simple example where you would put that in 0:14:02.320 --> 0:14:04.760 the wall, in the in the gap between the two 0:14:05.280 --> 0:14:07.240 sides of the wall, the two pieces of drywall. I 0:14:07.280 --> 0:14:09.720 saw one even saying denim. You can use different like 0:14:09.800 --> 0:14:12.920 fabric type, interialt or something like. The important thing is 0:14:12.960 --> 0:14:16.679 that whatever you use, you cannot pack two densely exactly, 0:14:16.760 --> 0:14:19.360 because if it's too dense, that's going to transfer sound 0:14:19.440 --> 0:14:21.480 and you're back to the same problem you were it before. 0:14:21.520 --> 0:14:24.160 And you also want to have still have some air 0:14:24.200 --> 0:14:27.520 gap there too. You don't want the material to make 0:14:27.560 --> 0:14:31.720 contact completely through the gap. You would pack kind of 0:14:31.760 --> 0:14:33.680 like half of the gap, a little more than half 0:14:33.680 --> 0:14:37.080 of the gap. Typically with insulating material, you leave an 0:14:37.080 --> 0:14:43.400 air gap, and that really creates a great cushion for sound. UM. 0:14:43.520 --> 0:14:45.360 We'll talk a little bit more about how that can 0:14:45.400 --> 0:14:48.760 go wrong though. Uh decoupling in particular can make certain 0:14:48.760 --> 0:14:54.040 things UM a little more difficult. There's also damping. Sound dampening. Uh, 0:14:54.080 --> 0:14:56.240 this is where you use some sort of material that 0:14:56.320 --> 0:14:59.960 resists vibration. So like the foam we have here, there's 0:15:00.040 --> 0:15:02.360 some we've got some dampening foam in here. But the 0:15:02.400 --> 0:15:04.880 typically you look at a lot of things like adhesives 0:15:04.920 --> 0:15:08.240 that are used to dampen sound. Um. One of the 0:15:08.240 --> 0:15:10.880 ones I keep hearing about over and over as green glue. 0:15:11.400 --> 0:15:16.200 Green glue is yeah, so so it's very popular, particularly 0:15:16.240 --> 0:15:20.920 apparently in Canada, but it's popular along amongst sound proving technicians. 0:15:21.160 --> 0:15:24.040 It is considered to be one of the most effective 0:15:24.720 --> 0:15:28.840 for the least amount of money solutions for sound dampening material. 0:15:28.880 --> 0:15:32.480 But typically this would be a layer that would also 0:15:32.520 --> 0:15:36.720 be part of your wall that resists the vibration of 0:15:36.800 --> 0:15:40.560 sound and so it won't transfer sound as well. Um. 0:15:40.760 --> 0:15:45.000 It's again, uh, something that you would apply between two 0:15:45.040 --> 0:15:47.520 constrained layers. So it's not like it's not like you 0:15:47.560 --> 0:15:50.600 would cope this on the interior wall. That would be 0:15:50.600 --> 0:15:53.360 a bad idea. It would be on the the the 0:15:53.480 --> 0:15:56.360 back side of the interior wall. It might even be 0:15:56.560 --> 0:15:59.600 something you could use as an adhesive for other sound 0:15:59.640 --> 0:16:02.840 damping materials like acoustic foam or tile. And then the 0:16:02.960 --> 0:16:07.920 last element is really the simplest, is mass. It's just 0:16:08.000 --> 0:16:11.520 that heavier things are harder to move than lighter things, right, 0:16:11.760 --> 0:16:14.280 It's just the basic idea like if if you had 0:16:14.280 --> 0:16:18.440 a cart filled with concrete blocks, it would be a 0:16:18.520 --> 0:16:20.480 little heavy to push, But if you had that same 0:16:20.520 --> 0:16:22.760 cart and it was filled with feathers, it's easy to push. 0:16:22.880 --> 0:16:25.080 So I've got something for you. He uses all of 0:16:25.120 --> 0:16:28.520 those elements in a pretty perfect example, one of the 0:16:28.560 --> 0:16:31.360 more perfect examples of soundproofing that we can see in 0:16:31.360 --> 0:16:34.000 the real world. I'm not sure I think Microsoft has 0:16:34.080 --> 0:16:36.480 maybe outdone them at this point. But there is a 0:16:36.520 --> 0:16:40.600 place in Minneapolis, Minnesota called or Field Laboratories and it 0:16:40.640 --> 0:16:44.200 contains um what was I believe again until recently, the 0:16:44.240 --> 0:16:48.280 world's most silent room. This world record for the most 0:16:48.320 --> 0:16:52.960 silent room. It is nine point nine nine sound absorbent. 0:16:53.480 --> 0:16:57.680 In order to accomplish this, it uses a combination of very, 0:16:57.800 --> 0:17:03.120 very very thick, heavy materials. It's got concrete walls, steel reinforcement, 0:17:03.440 --> 0:17:05.560 and then on the inside of the room. I'm looking 0:17:05.560 --> 0:17:09.480 at a picture right now, it has these alternating sort 0:17:09.520 --> 0:17:12.639 of thin looking things, so You've got like three and 0:17:12.680 --> 0:17:15.679 then going from left to right, and then three right 0:17:15.720 --> 0:17:18.960 next to it, going vertically, and they alternate throughout every 0:17:19.840 --> 0:17:22.840 panel in this room, um, and then even on the floor. 0:17:22.960 --> 0:17:25.399 And the what you stand on is a metal grate 0:17:25.560 --> 0:17:28.720 that goes on top of another series of these alternating, 0:17:28.880 --> 0:17:34.280 um little little units. And apparently, um, the longest anyone 0:17:34.359 --> 0:17:36.760 has been able to stand being in this room alone 0:17:36.800 --> 0:17:38.960 with the lights out is forty five minutes, because people 0:17:39.000 --> 0:17:43.200 start to hallucinate this level of silence. I've I've heard 0:17:43.240 --> 0:17:45.040 such things. It's the sort of thing every time I 0:17:45.080 --> 0:17:48.639 hear it, I have the reaction that I think people have, 0:17:48.760 --> 0:17:52.080 which is bet I could go longer, And of course 0:17:52.119 --> 0:17:54.199 I'd probably be in there for like three minutes and 0:17:54.240 --> 0:17:56.960 be convinced I've been in there for three hours. Because 0:17:57.240 --> 0:18:00.760 once you get to a point where something that you 0:18:00.840 --> 0:18:04.280 have taken for granted, you know, just the ambient sounds 0:18:04.280 --> 0:18:07.840 that you can hear once that's gone, that really does 0:18:07.960 --> 0:18:12.199 make a big difference. And uh, it is a psychologically 0:18:12.320 --> 0:18:16.120 powerful experience, but I still kind of want to do it. Yeah, 0:18:16.160 --> 0:18:19.120 that's a great way of of kind of summing up 0:18:19.160 --> 0:18:21.639 all of these elements. Now, if you want to really 0:18:21.680 --> 0:18:24.159 sound proof a room, the best thing to do is 0:18:24.200 --> 0:18:26.920 to incorporate as many of those as you possibly can, 0:18:27.040 --> 0:18:30.760 because they're different. Ones are good for different parts of 0:18:30.800 --> 0:18:34.160 that frequency range we're talking about, So some of them 0:18:34.160 --> 0:18:36.879 are really good for those mid too high range frequencies, 0:18:36.920 --> 0:18:39.080 some of them are a little better at the low frequencies. 0:18:39.400 --> 0:18:42.000 So obviously you want to have a good combination. Otherwise 0:18:42.040 --> 0:18:45.600 you're gonna have certain sounds come through even if you've 0:18:45.800 --> 0:18:48.600 perfectly blocked the room for other ones, and that can 0:18:48.640 --> 0:18:51.560 be really frustrated. Literally a cut off or a threshold 0:18:51.560 --> 0:18:54.920 where if you looked on a graph that can show 0:18:54.960 --> 0:18:59.760 you what frequencies are happening, you could literally track Okay, 0:19:00.119 --> 0:19:04.399 this frequency, now I can hear it. Yeah, it's that specific. Nolan. 0:19:04.480 --> 0:19:06.119 I will be back to talk a little bit more 0:19:06.119 --> 0:19:08.960 about sound proving, but first let's take this quick break. 0:19:16.560 --> 0:19:19.760 So kind of going back to to decoupling a little bit, 0:19:21.160 --> 0:19:23.919 The size of the air cavity between the two sides 0:19:24.000 --> 0:19:29.320 of the decoupled wall determines something called the resonant frequency 0:19:29.600 --> 0:19:33.000 of that. So here's the here's one of the problems 0:19:33.040 --> 0:19:36.879 with decoupling. That air cavity ends up acting kind of 0:19:36.920 --> 0:19:40.480 like a spring, right, So springs actually have a resonant frequency, 0:19:40.520 --> 0:19:43.800 and if you end up vibrating something at the resonant frequency, 0:19:43.960 --> 0:19:48.240 it causes that thing to vibrate very very easily. The 0:19:48.280 --> 0:19:50.879 big example of this that everyone is familiar with is 0:19:50.960 --> 0:19:54.920 the crystal glass. The opera singer hitting that note, that's 0:19:54.960 --> 0:19:57.080 the resonant frequency for it, and you can actually see 0:19:57.080 --> 0:20:01.000 the glass to form and ultimately break. Now or even 0:20:01.040 --> 0:20:03.040 someone that can play those glasses where they fill it 0:20:03.119 --> 0:20:05.280 up with water and run their finger around the rim. 0:20:05.880 --> 0:20:07.919 In order for it to start making that tone, it 0:20:07.960 --> 0:20:11.520 has to reach that resonant frequency exactly to basically self 0:20:11.560 --> 0:20:15.520 oscillate exactly. So so here's the problem with the decoupled 0:20:15.520 --> 0:20:18.080 walls is that that air gap, because it's acting like 0:20:18.119 --> 0:20:22.120 a spring, uh, and because it can resonate if it's 0:20:22.280 --> 0:20:25.600 not at the proper thickness for the air gap, that 0:20:25.680 --> 0:20:29.440 resonant frequency maybe within the range of sounds that you're 0:20:29.440 --> 0:20:32.000 going to generate either inside or outside the room, within 0:20:32.040 --> 0:20:34.240 the range of human hearing, which means they're going to 0:20:34.400 --> 0:20:38.800 impact that sound proving. And if something actually is played 0:20:38.880 --> 0:20:41.159 at that frequency, it will go not only will it 0:20:41.200 --> 0:20:43.320 go through the wall. It'll go through the wall more 0:20:43.440 --> 0:20:47.040 easily than it would have if you hadn't decoupled the 0:20:47.080 --> 0:20:51.399 wall because that resonance. Uh So that is one of 0:20:51.400 --> 0:20:53.399 the things you actually have to take into account. And 0:20:53.520 --> 0:20:56.840 one of the solutions to that is don't make it 0:20:57.000 --> 0:21:02.000 too thin of an air gap. Um. So another way 0:21:02.040 --> 0:21:05.560 of experimenting this with this yourself, if you want to 0:21:05.640 --> 0:21:08.480 just have some fun, and by fun, I mean, like 0:21:08.920 --> 0:21:12.240 you know, Mr Wizard style fun. You get a bottle 0:21:12.480 --> 0:21:15.680 and you know, if you blow across the the opening 0:21:15.680 --> 0:21:18.040 of the bottle, it produces a tone. Well, it doesn't 0:21:18.040 --> 0:21:20.640 matter how hard you blow, it's always going to play 0:21:20.640 --> 0:21:23.919 that one tone. But if you add water to the bottle, 0:21:23.960 --> 0:21:26.959 you have decreased the volume of air the bottle can 0:21:27.000 --> 0:21:29.400 hold and that changes the tone. Again. Back to the glasses, 0:21:29.480 --> 0:21:32.600 they could have, you know, the same size glasses, but 0:21:32.720 --> 0:21:35.639 they generate different tones from each one by putting a 0:21:35.680 --> 0:21:38.320 different amount of water in each right, Right, it's not 0:21:38.400 --> 0:21:40.520 just the size of the glass, but how much liquid 0:21:40.600 --> 0:21:43.359 is in the glass. So what you would love like 0:21:43.480 --> 0:21:48.320 to do is make sure that your soundproofing UM technique 0:21:48.680 --> 0:21:50.840 was going to take care of those maybe mid two 0:21:51.160 --> 0:21:55.639 high range uh frequencies and then make sure that the 0:21:55.680 --> 0:21:58.200 air gap would push would resonate at one of those 0:21:58.240 --> 0:22:01.400 frequencies so that the other elements of your sound proofing 0:22:01.520 --> 0:22:04.360 take care of it and it doesn't pass through. If 0:22:04.359 --> 0:22:07.800 your resident frequency is too low and you didn't really 0:22:07.800 --> 0:22:10.800 protect against that, it's going to pass right on in. Uh. 0:22:10.880 --> 0:22:14.840 So there's also something called the triple leaf effect. And 0:22:14.880 --> 0:22:16.879 I had to look this up in a couple of 0:22:16.920 --> 0:22:19.119