Shh! How Soundproofing Works

it was lovely. We actually recorded together yesterday for Stuff They Don't Want You to Know, which you are a host of that show co host, a co host along with the co hosts with Matt Frederick and Ben Bolan and you guys were very generous to have me on, and so I'm not as generous, so I only took one of you. That's fair. We had a good time though. We did a nice little Facebook live thing. We talked about targeted ads and got all riled up and then

recorded a nice little podcast. It was fun. Yeah. So if you guys have been enjoying my series on on the problem with advertising online, you can think of the Stuff They Don't Want You To Know as sort of a sister podcast on that same topic. Some of the stuff we cover is similar, but we take a because we have three other folks in there, and it's four people total. It ends up having a lot of different viewpoints and a lot of discussions, and we tend to

go a little dark at times. Yeah it does. It gets a little dark, um, but also fun also light. You know, it's not all the dark, suff I mean, it's it's it's life, right. So one of the things I like to do on this show is at the end of every episode, I invite you guys to send me requests ideas topics for future episodes. And today's episode is due to that. So I'm going to read a little bit of listener mail. You know, we used to have a whole claxon all right, here he goes, Hey

you tech stuff. First off, I want to thank you for putting out your content as I'm a huge fan of this casual learning movement. Might need a better term for that. I was wondering if you'd be able to do an episode on acoustics and sound dampening for studios, like how they're measured, tuned, made, etcetera. It would be awesome and spectacular as I would be able to harness the power to put together a kick ass set up. Thanks again for what you do. Dub Nosis well dubbed

we're going to do that for you. And that's really the reason why I asked Noel to come in here, because Noel, as a producer and sound engineer type person, has had real world experience with this, and so we're going to rely heavily upon his um perspective some of the stories he has to tell about the process of trying to make a room more soundproof or tuning a room so that you're getting the sound you want while you're recording, because, as it turns out, sound is a

pretty tricky thing when you boil it down. Sound is vibration, right, It's just particles banging together. It's a whole thing you gotta wrangle. It is a thing you gotta wrangle. We often consider sound to just be this thing we perceive with our ears, but what's really happening is a little more granular than that. Sound is particles that are moving, vibrating. Uh. Typically we're hearing things that are coming through over the air, like actual air around us. So you listening to this

right now, you can hear my voice. Well, what's actually happening is that some speakers are vibrating some air molecules, and that is compressing and decompressing those molecules. It's it's changing the pressure, increasing and then decreasing the pressure at frequencies and amplitudes that your ears pick up and then you perceive a sound. So this is happening through all

sorts of media, not just air. It can pass through solid matter, it can pass through liquid and depending on how the particles are packed and the space between them, sound may move better through one medium than through another. Now, knowing that sound can travel through different media, you also need to know that it can transfer from one medium

to another medium. So for example, if I'm shouting really, really loudly in a little room, some of that sound when it makes contact with the wall, actually causes the wall to move. Now it's not causing the wall to move a lot, but it is making the wall vibrate a little bit. Those vibrations get transferred through the wall to the other side. And that's why if you're in a place that has, you know, flimsy walls, you can hear someone in another room. The sound is actually transferring through.

Not to mention in the room itself, that sound is actually reflecting back at you, and the quality of the sound can depend. You can very greatly depending on the material that the room is built out of or treated with right, right, So some of the sounds getting transferred through the materials, some of the sound is being bounced

back from the material toward you, um. And a lot of that depends upon the the hardness of the material, Like a really hard materials and bounce a lot more sound back at you, which is why if you are in a large room with a lot of hard surfaces you get that echoe sound. Um. Or if you're out someplace like at a canyon and you do a shout and you get that echo back, it's because the sound is going out hitting the walls of the canyon, bouncing back to you, and that's when you get to experience

that effect. Well. Obviously, this means that if you want to create a place where the sound can't escape or leak into and a lot of recording studios, you want

both of those things right. You don't want the sound from the studio to leak outward, but you also definitely don't want outside sound to leak into the important Then you have to figure out, well, how do we limit how do we work within the physical uh uh constraints of the way sound works, so that we can limit that as much as possible and try to have the

purest experience as we can. Uh So, one thing you can remember is that sound, because it's a physical activity and because it relies on on energy, the way it works is that you've got a source of the sound. Sound waves travel outward concentrically outward from that source, and they get weaker as they travel out that that energy starts to dissipate. You can think of it kind of like um uh, you know, each each time a particle has to bang up against another one to move it,

some of that energy ends up getting lost. So the further way you are from a source of sound, the quieter it is. That's why that happens. So one way you can limit the way sound comes out of a room is you make an enormous room like you have a little room in a really big room. Um. But that's not necessarily the most practical approach. Actually, there's a studio I used to intern at in Athens, Georgia called Chase Park Transduction, and they essentially built their studio inside

of a larger warehouse space. So they're renting a space in the strip of big giant, very high ceiling warehouse spaces. But when you go into the studio, you're in the warehouse. But then there's a smaller basically building inside that warehouse that is the one that receives all the acoustic treatments. But it's like you said, I mean that is one way of dealing with it is air. Yeah, the room within a room approach is often how it's referred to,

and sometimes it is not as obvious as that. Like it may be that it looks like the the room you're walking into might be like it's it's in a little uh alcover hallway, but that hallway is actually showing where the the walls are, where there's an air gap between the two walls to to mitigate any sound coming

into the space. Even this glass window that we have in the booth that we're recording in right now, it's a double paned window, So in between these two relatively thick pieces of glass is a little layer of air, which in and of itself acts as a bit of a sound dampening insulation device, right exactly, So, uh, some other little elements of sound that we need to remember. There are two main components to a sound wave. That are important to keep in mind. One is amplitude or volume.

So if you are looking at the way we typically show a sound wave which is on like an X versus Y graph um you know those those sine wave style graphs, the height and depth of the troughs that represents the amplitude how loud the sound is. Then you have the frequency of sound, the number of times sound cycles within a second. That determines the pitch of a sound.

So a low frequency obviously would be a perceived as a lower deeper note or tone, and a high frequency, with those peaks and troughs moving gradually more closer together, is going to be perceived as a higher pitch. A good way to think about this too, is if anyone's familiar with the instrument the theoremin. There are two controls

on a theoreman. One is the antenna that goes upward, and there's an end and on the side uh the antenna on the side you use your hand by moving it closer to or farther away, you are changing the amplitude and that's perceived as a change in volume. The antenna going up as you move your hand closer to it or farther away, you are changing the frequency. So with those two controls you can basically shape the way

the sound is perceived. Right, And it's important to remember these things because uh, as it turns out, different approaches to sound proofing are effective for different frequencies. Definitely, right. So there might be one that you're like, oh, this is this is perfect. I can't hear my neighbors anymore. But then it turns out that when your neighbors put on a an album that has a lot of base in it, it comes right through or start yelling at

each other for whatever. Yeah, the amplitude is loud enough, it maybe that you're soundproofing isn't going to be. Uh. When people yell, sometimes they tend to raise the picture right right right, the pitch goes up enough that I

got you. Yeah, So these are things that you have taken to consideration if you're trying to sound proof, and obviously what you are trying to accomplish, like the reason why you're soundproofing, that will play into it as well, because if all you're trying to do is just make it quieter so that you know, you don't have like you're designing a building, maybe it's a hotel and you want to make sure that the the people talking in one room doesn't bleed over into other rooms. That's one

type of soundproofing. If you're trying to make a professional recording studio, that's another type. From a construction standpoint, Like the base level soundproofing is drywall, so you have drywall, and that is where if you're in a hotel that only uses drywall, people are gonna be able to hear every single thing that's going on next door. It's when you start basically stuffing that dry wall with other denser materials or you know, highly rated soundproofing materials, that's when

you can really cut down on that transfer between the rooms. Right. And also there are other some other techniques you can use as well that I'll get into that, And it's all about how do you make it harder for the sound to travel from one place to another because sound is going to travel no matter or what. It's not like we have created a material that just sucks up sound totally. We've got a lot of materials that resist vibration and that means that they don't transfer sound very well.

But in fact, the studio has some of that around us. But you know, there's other stuff you have to take into consideration as well. Now, there are four general elements to soundproofing, and we've we've kind of touched on a few of them, but one of the big ones is called decoupling. Now, decoupling is a construction term. When you're talking about decoupling, you're talking about the way the walls of the soundproofed area are actually constructed. So you were

just talking about dry wall. The typical way a wall is constructed if you've got studs and attached to the studs are the anchor points for the drywall. And in a typical wall, the studs are connected on either side by drywall for one side of the wall and dry wall for the other side of the the wall. So the uh and if you can think of it like the

interior wall versus the exterior wall of a room. The problem with that is that when sound hits the drywall, then sound can travel through the dry wall through the studs, which transmit sound. They're a pretty good conductor for sound to the other side of the dry wall, and then you get sound bleeding out or you have sound bleeding in from the outside. So decoupling is a process where you would build a wall so that the studs don't

touch both sides of the wall. You would have a series of studs that one side the interior wall are attached to, and a different series of studs that the exterior wall are attached to. They both extend well into the gap between the two walls, but they don't touch

the other side. So one side could be receiving sound waves and potentially transfer those, but since they're not touching, it's much more difficult for that to happen, right, because air is not as good a conductor of sound as a solid object is, which you wouldn't think that, because I mean, here we are in a room talking to each other, and the air is basically what's connecting us. But the interesting thing, though, is that the way you

can tell this, it's very easy way to tell. It's the old kid game of a telephone where you get two cans in a string. Right, You you punch holes in the bottom of the cans, You run the string through the holes, you stretch it taut, and then you can whisper into one can and hear it on the other side. But if you whisper that same volume across

the room you can't hear it. So again that shows that the the physical media is actually more or medium I should say, is actually more efficient at transferring the sound than than air is. So air pockets are actually really important when you're soundproofing, you know, designing a soundproof room. UM. Typically you would pair decoupling with some of the other elements, and I'll go ahead and mention what those elements are, and then we'll talk more about how you would put

it all together. So you've got absorption another important element. This is obviously using a material that slows down sound. Uh It absorbs some of the sounds, so that sound essentially loses some of its energy and it thus is quieter. It doesn't it doesn't leak out as much because the amplitude gets reduced as a result. Uh. So absorption you achieve usually through using some sort of insulation material like UM.

I mean fiberglass is a simple example where you would put that in the wall in the in the gap between the two sides of the wall, the two pieces of drywall. I saw one even saying denim. You can use different like fabric type, interial, cotton or something like. The important thing is that whatever you use, you cannot pack two densely exactly because if it's too dense, that's going to transfer sound and you're back to the same problem you were it before. And you also want to

have still have some air gap there too. You don't want the material to make contact completely through the gap. You would pack kind of half of the gap, a little more than half of the gap. Typically with insulating material, you leave an air gap, and that really creates a great cushion for sound. UM. We'll talk a little bit more about how that can go wrong though. Uh. Decoupling in particular can make certain things, um a little more difficult.

There's also damping sound dampening UH, this is where you use some sort of material that resists vibration. So like the foam we have here, there's some we've got some dampening foam in here. But the typically you look at a lot of things like adhesives that are used to dampen sound. UM. One of the ones I keep hearing about over and over is green glue. Green glue is yeah, so so it's very popular, particularly apparently in Canada, but

it's popular along amongst sound proving technicians. It is considered to be one of the most effective for the least amount of money solutions for sound dampening material But typically this would be a layer that would also be part of your wall that resists the vibration of sound and so it won't transfer sound as well. Um, it's again, uh, something that you would apply between two constrained layers. So it's not like it's not like you would cope this

on the interior wall. That would be a bad idea. It would be on the the the back side of the interior wall. It might even be something you could use as an adhesive for other sound dampening materials like acoustic phone or tile. And then the last element is

really the simplest is mass. It's just that heavier things are harder to move than lighter things, right, It's just the basic idea like if if you had a cart filled with concrete blocks, it would be a little heavy to push, But if you had that same cart and it was filled with feathers, it's easy to push. So I've got something for you. He uses all of those elements in a pretty perfect example, one of the more perfect examples of soundproofing that we can see in the

real world. Um, I'm not sure. I think Microsoft has maybe outdone them at this point. But there is a place in Minneapolis, Minnesota called or Field Laboratories and it contains um, what was I believe again until recently, the world's most silent room. This world record for the most silent room. It is ninety nine point nine nine sound absorbent. In order to accomplish this, it uses a combination of

very very very thick, heavy materials. It's got concrete walls, steel reinforcement, and then on the inside of the room, I'm looking at a picture right now, it has these alternating sort of thin looking things. So you've got like three and then going from left to right, and then three right next to it, going vertically, and they alternate throughout every UM panel in this room, UM, and then even on the floor. And the what you stand on is a metal grate that goes on top of another

series of these alternating UM little little units. And apparently, UM, the longest anyone has been able to stand being in this room alone with the lights out of forty five minutes because people start to hallucinate right this level of silence. I've I've heard such things and it's the sort of thing.

Every time I hear it, I have the reaction that I think people have, which is bet I could go longer, and of course I'd probably be in there for like three minutes and be convinced I've been in there for three hours. Because once you get to a point where something that you have taken for granted, you know just the ambient sounds that you can hear once that's gone, that really does make a big difference. And uh, it is a psychologically powerful experience, but I still kind of

want to do it. Yeah, that's a great way of of kind of summing up all of these elements. Now, if you want to really sound proof a room, the best thing to do is to incorporate as many of those as you possibly can, because they're different. Ones are good for different parts of that frequency we're talking about, So some of them are really good for those mid too high range frequencies. Some of them are a little better at the low frequencies. So obviously you want to

have a good combination. Otherwise you're gonna have certain sounds come through even if you've perfectly blocked the room for other ones, and that can be really frustrated. Literally, a cut off or a threshold where if you looked on a graph that can show you what frequencies are happening, you could literally track Okay, at this frequency, now I

can hear it. It's that specific usually, so kind of going back to to decoupling a little bit, the size of the air cavity between the two sides of the the coupled wall determines something called the resonant frequency of that. So here's the here's one of the problems with decoupling. That air cavity ends up acting kind of like a spring, right, So springs actually have a resonant frequency, and if you end up vibrating something at the resonant frequency, it causes

that thing to vibrate very, very easily. The big example of this that everyone is familiar with is the crystal glass the opera singer hitting that note, that's the resonant frequency for it. You can actually see the glass to form and ultimately break. Now, or even someone that can play those glasses where they fill it up with water and run their finger around the rim. In order for it to start making that tone, it has to reach

that resonant frequency exactly. Basically self oscillate exactly. So, So here's the problem with the decoupled walls is that that air gap, because it's acting like a spring, uh and because it can resonate if it's not at the proper thickness for the air gap, that resonant frequency maybe within the range of sounds that you're going to generate either inside or outside the room, within the range of human hearing, which means they're going to impact that sound proving it

if something actually is played at that frequency, it'll go not only will it go through the wall, it'll go through the wall more easily than it would have if you hadn't decoupled the wall because that resonance. Uh So, that is one of the things you actually have to take into account. And one of the solutions to that is don't make it too thin of an air gap. Um So, another way of experimenting this with this yourself, if you want to just have some fun, and by fun,

I mean, like you know, Mr Wizard style fun. You get a bottle and you know if you blow across the the opening of the bottle, it produces a tone. Well, it doesn't matter how hard you blow, it's always going to play that one tone. But if you add water to the bottle, you have decreased the volume of air the bottle can hold, and that changes the tone. Again. Back to the glasses, they could have, you know, the same size glasses, but they generate different tones from each

one by putting a different amount of water in each. Right, it's not just the size of the glass, but how much liquid is in the glass. So what you would love like to do is make sure that your soundproofing UM technique was going to take care of those maybe mid too high range uh frequencies and then make sure that the air gap would push, would resonate at one of those frequencies, so that the other elements of your soundproofing take care of it and it doesn't pass through.

If your resonant frequency is too low and you didn't really protect against that, it's going to pass right on in UH. So. There's also something called the triple leaf effect. And I had to look this up in a couple of different locations to find out what the triple leaf effect is because I don't know if you know this, Knuel. I haven't built any houses recently. So the triple leaf effect is all about a construction of a wall like a drywall, and they refer to each sheet of drywall

as a leaf. So you've got the interior wall that is one leaf. You've got the exterior wall. There's a second leaf. In a triple leaf approach, you actually have a third sheet of dry wall that's in between the two. It's inside the wall. It's further compartmentalizing it essentially, right and uh. And you might do this and think, oh, well, that's going to end up protecting against sound even better.

Not necessarily, um, it actually can cause a problem because it can create if the air cavity between the middle leaf and one side is too small, it can create those resonance problems. So people actually referred to as the triple leaf problem. So this is not necessarily a technique

you want to go for. This is describing a problem. Yeah. Yeah, So there are some proof technicians who say, if you have a triple leaf wall and you're having these resonant issues, the the solution is actually to tear open the wall. Remove that triple leaf, that third sheet of drywall, the one that's in between the other two. Take that out, and then it will create a thicker air gap between the two sides, and that will end up changing the

resonance problem. I because I could see that, I mean, does introduce more of a variable into the equation and as opposed to just having to having a third one, there there is more ways the sound could potentially bounce around or catch that resident frequency right And you know, um, we talked a little bit about echo and about how sound can bounce off of hard services that we talk about the bunny Men. No, we didn't talk about the bunny Man. You know they're playing in Atlanta soon? Are

they really? Wow that? I would much prefer to see them than insane clown posse you're already missed insane clown Know they played earlier this week, yesterday before day before yesterday. Yeah, I actually wanted to invite them over so we could explain how magnets work. But that's that's neither here nor there. No no in their heart, I hope so well, you know they made a whole video about it. But the echoes can be an issue obviously in recording studios, things

like that. You don't want there to be if there's gonna be any echo, you wanted to be there on purpose, not because of just that's the way the room was built same here for our studio. We don't want too much echo here, and we are in a building that's made out of concrete. Now that in some ways that's good because it helps dampen sound from other areas. Unless something is making direct contact with the concrete, then we

can all hear it everywhere. Like whenever there's construction going on, you can hear it move through the concrete columns and floors and ceiling. It is disturbing their we play the

game what construction equipment? Do you think that is? Sometimes you just don't know because the sound can mutate based on what it's vibrating to, you know, right, it might be a little drill that's vibrating a giant piece of metal, and then that's vibrating something else, and by the time it gets to us, it sounds like there's a giant playing hop scotch ups there. Yeah, it could be a

little distracting. Fortunately, most of the spaces in in the building where in now have been built out because when we moved into this building, we were one of the first offices here. Yeah, and that just meant that we had construction noises pretty much consistently throughout the whole experience, so that is been reduced dramatically over time. But one of the other things is that you know, we when since we have all this concrete, we have to figure

out how to eliminate that echo. And the way you do that is typically by putting softer material on top of the harder material and that that again dampens the echo. So uh, you know, if you if you have a castle, you probably are hanging tapestries for a couple of reasons. One, it acts like an insulator so you don't lose as much heat in those cold winters. And do when you're screaming at your servants because your food isn't on the

table when the bad guys are attacking your castle. Yeah, you want you don't want that to echo throughout the castle unless you're a villain. And when when I'm decorating my castle, I tend to go with tapestry. I do. I do too. I'm I'm tapestry heavy when I do that. Um, but it's it's so sore of stuff You can do inside like a home studio too. You can hang uh fabric, heavy fabric to help kind of like a theater style curtain is excellent. Not only because of its of what it's,

the denseness of it. It bunches up like so you can kind of squeeze it together where it creates these natural kind of ripples which not only absorbed the sound, they sort of diffuse it a little bit in the same way what I was describing with that World's Quietest Room. These alternating patterns of material that have little spaces in between them, they act as a diffuser for the sounds. Right. And there's there's one other thing that we can talk about,

or i'll briefly mention, which is sound cancelation. That's a little different from soundproofing. Actually in a way, it's the opposite because you actually have to create sound with sound cancelation. The way sound cancelation works is if you were to look at that that graphic representation of a sound wave, Let's say it's a steady tone, because that's the easiest

way to imagine it. So it's a stay tone it I don't know, three hurts, and you're looking at a three hundred hurts sign wave, and you see where the peaks and troughs are. If you were to create a a complementary sign wave where it is out of phase, so the peaks and troughs match up with the troughs and peaks, then they cancel each other out. That's the crazy thing about sound, because you typically think if you

add more sound to sound, it just gets louder. Like if you've ever been in a restaurant that has lots of hard surfaces, it becomes really difficult to have a conversation if it's a busy night because everyone everyone starts to talk over everyone else and it just kind of echoes. Well, it turns out that if you do add sound to sound, but you make sure it's out of phase, it cancels it and then it's as if there's no sound at all.

That's what noise canceling headphones do. They create a sound, they detect the incoming sound waves, they create complimentary sound waves that phase that out, and then you get silence as a result. So an example of that phenomenon that you don't want that actually has to be corrected. If you're in a recording studio. Let's say you're recording an acoustic guitar and you want to mike it in two places, so you might put a mic on the soundhole of the acoustic guitar that you might want to put a

mike a little further up on the next somewhere. If those mike, since they're recording the same signal essentially, but they're spaced apart, there is the potential for phase issues between those two mics. So while it's not going to get straight up cancel out the sound, it's going to change the quality of the sound in a way that you might not like. It might make it tinier, or it might give it almost like one of those phaser kind of a jet engine psychedelic guitar type sound. You know,

you know where it's filtered through that sound. Um, So what you have to do is you can you can correct this after the fact, but there are devices that you actually can test the phase at the point you're recording and then space the mics apart accordingly, And there's even ways to adjust the phase using these devices. So it's interesting how you're describing as sort of a practical use of this phenomenon. And then there are also versions of that happened in a recording situation that you actually

have to be careful you have to correct for. Yeah, So for for soundproofing, there are a couple of different UH measuring systems to determine how soundproofed a room is, and they may or may not be useful to you if you are trying to do something like create a

recording studio. So, for example, in the United States, we typically use something called the sound transmission class to explain how soundproofed a room is, and that's really a measurement of how well sound within the ranges of human voices

travels through walls. So sounds outside of those frequencies, it sound transmission class isn't concerned with them, because it's really more about building walls so that sound doesn't pass or walls and floors and ceilings, not just walls, but all the all the surfaces so that sound does not pass easily through one UH and into another. This would be like what hotels would be really concerned with, or people

who are building homes. UM that range, by the way, is about hurts to four thousand hurts or four killer hurts. That's the that's the typical range of frequencies of the human voice. So that's really what sound transmission class is concerned with. And it's designated by a number, and in general, the higher the number, the better the quality of soundproofing is.

So if you were in a room that has like a really kind of lousy dry wall partition, it doesn't have a whole lot of you know, like it doesn't have that that absorption installation or anything like that. Uh, the number might be somewhere around twenty. But let's say you're in a high end hotel that has taken great pains to create decoupled walls with good absorption insulation some maybe some dampening material in there too, that might be closer to sixty. And so the higher number designates it's

more sound proofed than the other one. But again for that given range of frequencies. The stuff outside of that maybe not so much. Outside the United States, people tend to use was called the sound reduction index. Uh, it's it's the s r I. So that rating tells you

how many decibels in reduction the material will provide. So if a sound is a certain amplitude, a certain amount of decibels, which by the way, is not a not a it's a logarithmic scale, so it's pretty complicated, but it will tell you how many decibels it will reduce. A sound that is generated from one space and into

an adjoining space. UM. It's depending also upon frequencies because some are designed to it's it's something that's specifically designed to cut out those mid to high range frequencies, but it won't necessarily uh like that material won't necessarily cut out low frequencies. So if you get this s r I number, you have to also ask, well, what what range of frequencies is that for? Because it's not a blanket statement. It's not saying that any sound at any

decibel will be reduced this amount. Then you finally have noise reduction coefficient. Uh. So this tells you how much sound of material can absorb versus reflect UM. It's it's expressed as a percentage, So really the percentage that you're looking at is the percentage of sound absorbed by that material. A carpet with a rubber underlay might have a point for rating. For example, that means it would absorb of

the sound that hits it reflecting back. UM Like a hard concrete wall might be a point oh five, meaning it absorbs only five percent of the sound that hits it and gets reflected back. So uh those are those are how you would you know that's like the metrics you would use. You would use actual instrumentation to detect how the sound is reverberating in the room. And you would you know, obviously use things like microphones and stuff outside of a room to detect if there's any sound

leaking out. There are also some things you gotta take into account, um, some natural weak spots. If the room has a vent in it, which you kind of hope it will because otherwise things get real stuffy, real fast. Uh, the vent also may need to be treated. Ideally the vent will be treated with some of this material to dampen some of the sound. Otherwise it's just a conduit for sound to travel through. Yeah. So the room we're recording in right now, it was built out for us

with some of these specs in mind. Um. We chose the material based on the rating and we went with

obviously a higher number UM. And then this glass window that I was telling about earlier that's specifically designed for a studiotype environment, and what we have on the walls in here are similar to the layout of that World's Quiet room most talking about, except these are acoustic tiles that are made up of their squares and they're made up of strips in a single direction, but the panels are alternating, so we have one where they're facing up and down, the one next to it they're going left

to right, etcetera. And they altered it and that helps break up the sound and um, you know, make it a more uh dampened sound within the room and keep the sound from escaping as well. But we actually do have event in this room and it's not particularly well treated. So what I actually end up having to do is use a very nifty bundle of software to take a print of the room tone, so you can there's a base level where Jonathan and I were quiet right now,

you probably and we sent this out. Without running this process, you would hear that base level room tone, air conditioning sound, whatever. So what I can do with the software is analyze thirty seconds a minute, the longer the better of that baseline sound than the computer analyzes that, and then I apply it to the whole audio file and it gets

rid of it and no artifacting at all. Like when I want to say artifacting, I mean there's no digital debris leftover where you can hear, Oh, there here's the sound of the effect working. It's completely transparent and this sweet software is about two thousand dollars, so right, they're a really good job. There are a lot of software packages out there that that attempt to do something similar to that, like a Audacity has the noise Removal tool,

which is a very similar thing. It's looking at specific frequencies and then it looks through the entire track or those frequencies to remove those. Problem is, of course, that if you have other stuff laid on top of it, Audacity doesn't necessarily it's not necessarily able to go in and remove just the stuff that you want removed and leave everything else untouched. So uh well, my experience with things like this as has always been now it doesn't work.

You can always tell, you can always hear it kicking in or whatever. But just in case anyone's interested in, the software I'm talking about is by a company called Isotope, and it's a package called r X Advance, and it's a suite that has multiple um little modules that can do different things like let's say you're picking up a hum or some kind of radio interference. It can is isolate things like that. But the one I always used to give to that air conditioning noise is it's called

de nois er and it's it's it's fantastic cool. And the other thing that you have to worry about besides the vents are obviously doors. You want to have. Make sure that your doors have proper ceiling all around it.

Ceiling S, S, E A L. That kind of seal. Yeah, Like in a recording studio control room, you might see a door that has a heavy rubber um strip on the bottom of it that when you close it, it literally makes a seal between the door jam and the bottom of the door, so it's air tight, yeah, because otherwise sound will just travel underneath right underneath it. Yeah, the gap. You've done all this other work and then you have a gap in the bottom of your door,

you might as well have done nothing right. It's it's not gonna it's not gonna give you the results you want. So no, you know, we were talking before we start recording that, you know, the the concept of making sure the sound within a room sounds right, and this goes beyond soundproofing, but it was also part of of the question sent into us. So walk us through kind of

the process. If you were setting up, say a recording studio for music that would be obviously you would want to make sure that everything is just right to capture the music as the artist intended. You know, you might do some alteration on it on the back end, but you want it captured as pure as possible at the recording session. Yeah. This this goes into kind of recording philosophy. In some ways. Some people might want more of a live room that has some character, some nice acoustics or

something like that. And for certain things, like say recording a vocal, you might want a room with as little character as possible. So you're just getting the quality of that voice through that really nice microphone and microphone preamplifier, which is what you plug a microphone in that kind of boost that signal and makes it audible and makes it at a level that can then be recorded into the computer or tape machine or what have you. Um.

So that's one way of looking at it. Like for a quiet room, like a completely dead sound booth, let's say, Um, then you might have different little tricks you can do. Like so at a drum room, for example, there are ways you can use panels of wood on the floor. You might take a strip of wood and place it right underneath the kick drum the bass drum, and have a microphone kind of at the end of that, so you're the sound of the drums are sort of reflect day off of that wood and creating kind of a

cool diffuse room sound. So you when you mike drums, you're making them up close. You're putting a microphone right up on the tom tom or the snare of the kick, and then a lot of times people will mix in the sound of the room, which is the whole kit, and then kind of blend those signals together so you get that direct sound, which you also get this nice

roomy tone. So in that situation, you might want a little character in your room, and you might use things like I'm talking about these strips or what have you to achieve some sort of character. Now, let's say we're talking about a control room, which is where you're going to be mixing your your music. So you have really high end, very nice, high fidelities studio monitors which gives you your playback. And you know, the best studio monitors

are considered to be very um flat. That's that's the word that's used where the frequency response isn't particularly um it's not. It's not messed with on the speaker side. So everything that's coming out of there, you know, is going to be accurate based on what you're doing, what you're putting into it, the frequencies you're adjusting on your mixing console or in your computer. The monitors themselves aren't imparting any tone or quality beyond what you're doing to

it right there. They're just they're just neutral and only presenting the stuff that you've told it to a lot of times they're referred to as reference monitors because you the idea is, and it's not always the case, um that the way it sounds on those monitors, it's going

to sound like that anywhere you play it. Obviously, there are things that happen after you finish a record called mastering, where you you kind of adjust to account for different types of systems that might be played on to make sure it sounds as good as possible on any system. But in a control room when you're playing back your music, you don't want bad reflections. You don't want that sound coming out of the speakers to bounce back at you in a way that changes the quality of that sound.

You want it to be as flat and clean as possible. So there are little extra touches you could put in a control room that absorb certain frequencies. Like you said,

certain materials will absorb certain frequencies better. There are things you might put in the back corners of the room that fill up a corner where two walls meet, called base traps, and they are these kind of tall they can be round or squared off um and they're made of kind of dense fibroglass material covered in a particular type of fabric, and those absorb some of those base frequencies so that it's not bouncing back at you and

muddying up your mix. Then you might have a lot of times you'll see in a recording studio in the control room where you have your big mixing console, and

then directly behind it can still wall. A lot of times there's a couch, and then above that couch there might be a weird looking wooden panel that has smaller arrays of these alternating little um tiles sort of like what I described we have in our room here, but smaller and and a little more dense, And those are designed to do different things to other frequencies, like the mid range or the high UM. Another thing that's really important in uh these control room settings is where the

monitors speakers are placed. So what you might do is have an engineer UM that specializes in you know, do building out recording studios and tuning room as what they call it. Go in there and use a device that that measures the way frequencies bounce around the room, and you would generate what's called a test tone or uh some white noise even UM which is just like you know, static kind of sound. And then you can use this device, this handheld device, it might be cooked up to a computer.

There's lots of different ones UM that will then take a print and analyze, Okay, this is what the sound's doing. This is where this room needs some work, where we need to move the monitors a little further away or a little closer to the wall, et cetera. So that's just a few of the ways that you can UM affect how the sound is actually heard within a room for different situations, whether you're recording, whether you're mixing and listening,

it's all about that. There are different scenarios that require different treatments. Sure, and and anyone who's listened to you know, live albums versus studio albums, or for me, even just with classical music, Like if you ever listened to classical piece that was recorded in a big sound studio where you know, they got the whole orchestra in there, it

can sound really amazing. But then if you hear the same sort of thing but it's played in a concert hall even without an audience, the effect is measurably different. You get that character you were talking about of the space, and different spaces have very different characters. Just as musicians may have a favorite type of amplifier that they like to use because of the tone that it helps, uh, the tones that accentuates versus the ones that it doesn't

accentuate as much. Uh, you have the same sort of stuff with these these rooms. Now, no, let me ask you this. Let's say that some of our listeners out there are wanting to set up like a little home recording area. Maybe they want to do podcasting, maybe they

want to record some acoustic music, nothing too complicated. What would be some general guidelines you would give somebody who wants to set up a space in their house meant for recording, Like, what were what would just be some general tips, not like the super like you're gonna go and remodel your home kind of approach, but but more simple ways that you can at least limit problems with sound from exterior sources or uh interference with the sound that you're creating in the room. What are some of

your tips you would give. I mean, there's a lot of different ways that you can um make spaces in your home work, and all depends on what kind of music you're trying to record. Um So, the choice of microphone would make a big difference. For example, so the microphones that we use in the podcast studio or what are called dynamic microphones, and then we've talked about this

in the past episode. I believe um they tend to record best things that are very close to them and don't necessarily pick up as much ambient room sound as what's called a condenser microphone would. Now some might say that a condenser microphone gives a richer, bigger sound, but it also depends on how you use it. Um So, I might recommend for recording vocals trying to go with like get a really nice dynamic microphone, like one of these a Sure SM seven B microphones will use and

there you know, they're about three hundred bucks. They're not cheap, but um, they allow you to record uh much closer proximity. So if you're recording a guitar, for example, through an amplifier, you put it right up next to that amplifier and crank it so that it's not recording the signal to noise ratio is what's called is in favor of the signal, So the sound of the amplifier is uh the main concern.

There's really no worry about recording any room tone. And you don't even have to crank the amp up that high because the mic is so close. But in terms of little things you can do for dampening, I mean, get get a pack of egg crate or like some acoustic tiles from or Alex you know, and it's not either, but then just make some little clusters, you know, make a few little squares on your wall if you can, like if you have a closet door, maybe put three

or four panels and then record facing that, you know. Um, there are also these shields you can get you can attach to your mic stand and basically is like a um almost like a half moon shaped shield that goes behind the microphone so you're facing it and that cuts down on reflections. Um. There are lots of little tricks like that that you can do. But at the end of the day, UM, it's just about how you use the stuff that you have for podcasting. Definitely go with

a dynamic microphone. Talk very close to it so that it's only getting your voice and it's not recording your cats or the sound of your conditioning things like that. UM. The lower you can turn up the mic and still get a really good signal, the better off you are, because if you have to crank it up really high, you're really far away from the mic, you're gonna be picking up a whole lot of that room sounds. Yeah,

I I can tell you from experience. I record a couple of shows from home just for fun that that aren't work related. And I used to use a condenser mike because they were they were easy. I had a USB condenser mic. Um, and and there's nothing wrong with the MIC's. I'll even tell you I had a blue snowball for a while, and we have one here. We we've used it occasionally, mostly to connect through Skype or whatever.

We don't record through it, but we use it to to pick up our voices so people on the other end can hear us um. And I also had a blue Yetti microphone. Both of them are great. I love them, but for podcasting, like you were saying, they pick up

pretty much everything. And in fact, if you were to go back and listen to some of those podcasts I did, you would hear, like, what's that weird clicking noise of marrying in the background, And that clicking noise would have been my dog's toe nails clicking against the hardwood floor as as he just ran across the floor and he wasn't making any other noise. It's just clickick. But that condenser mike picked up everything. And it all comes back to what we talked about sound being sort of this

organic ing that moves. I mean, you're never going to completely get rid of every bit of room noise unless you are going above and beyond. You're going to that crazy world's most silent room approach. But you can mitigate how much of the sounds you don't want are recorded based on where you set up the mic. You want to be as far away from any noisy sources as possible.

You certainly wouldn't want to record a podcast right next to your fridge if you have an option, uh, if you have an internal room where it doesn't share an external wall, that would be a good choice. UM, Like like the place where my microphone is set up. I don't have a room that's enter. All of my rooms face outward one way or the other, so I don't have a room that I can that is that is

isolated where I could record from. UH. So my mine is not ideal because I also live across the street from um railroad tracks and Marta tracks uh and a busy road. So I'm just fortunate that when my house was being built, they built it with that in mind. They were building the external walls so that they would dampen that sound as much as possible. Because the home builders new while we're right next to some train tracks, so we have to take that into account when we're

designing this. Unfortunately, it doesn't often impact my recording. Once in a blue moon, if there's a freight train going by blasting its horn, you're gonna hear it, But otherwise it doesn't come through. So just to wrap up on this whole, you know, home podcast set up. I can give you a really good practical example of our show Stuff You Miss in History class Um. The host live in different cities. Holly Fry lives here in Atlanta and records in our studios, and Tracy Wilson lives in Boston

and records from her home. And so when she was getting ready to move, we had to figure out how we were going to set this up. So I kind of looked into it and did some research and recommended what to get, and what we ultimately went with is she has this. It's called the sound shield, I guess is the best way of referring to it. H A company is called SCLA Tronics. The product is a reflection filter ex portable vocal booth, and the idea is that the way it's pitched on on Sweetwater, which is the

music equipment site that I'm looking at. UM, it is a portable acoustic treatment to reduce room ambience in untreated recording spaces. So it works pretty well as advertised. So it's this thing that kind of wraps around the back of the microphone connects to the mic stand. UM. So she has one of those behind her against the wall. She has a heavy curtain like we talked about earlier as well, and so that helps dampen the sound that way. Uh,

And she's using this sm seven b um dynamic. Sure vocal mic or microphones doesn't have to be a vocal mic. But she is next to a window. So whenever the trash pick up comes, or if there's a motorcycle or something like that, you know, we've got to stop. So you deal with what you have. And I think she's a pretty good example of a successful home set up

as well as as as is yours. Jonathan. Yeah, if you if you listen back to um some of the episods that we recorded before we moved to Pont City Market, there was a brief period where we were set up in an office, uh like an actual It wasn't designed to be an audio recording studio, but was an office at the old office space and Buckhead that shared a

a window facing Peach Tree or near Peach Tree. And if you listen carefully to some of those old podcasts, not just Tech Stuff but all the other ones we record at How Stuff Works, you might occasionally hear a little high pitched noise and wonder what that was, And that was Baton Bob. There was also sirens. Those were the bane of our existence. Yes, sirens we would stop for like we if we heard the siren whistle. Baton Bob. Yeah, Beaton Bob is a a kind of a fixture here

in Atlanta. He is quite the character and often can be seen marching up and down the various streets of Atlanta in a tutu and twirling a baton and blowing a whistle. And he's a smile ambassador. I love Baton Bob, Absolutely love him. Great guy. Uh not fantastic to have to record a podcast. What you're hearing is in whistling up and down the street and talk about d I

y setup. We had those windows covered over with I made these panels out of that pink panther foam insulation for construction, and I nailed them and stapled them to pieces of luan and then had them attached to the window to cover them over. And then on top of that we had this bright red um acoustic foam in sheets that we you know, staple on top of that and it still didn't block out. And we couldn't do anything permanent because that that wasn't something we were allowed

to do in that space. It wasn't meant to be a recording studio, so we were just doing the best with what we had. Um but yeah, it was it was. It was difficult, so it can be a chance lenge. But the stuff is out there. It's not like like Noel is saying, it's not necessarily cheap. You can do some relatively inexpensive things to limit U sound issues, but obviously you get what you pay for the more that you are able to spend on that. But do your research.

But the more you're able to spend on that, the better result you are going to get. In general, just make sure that whatever outlet you're going with is highly rated, you know, don't just hire a general contractor and and go with that, because that's probably not gonna give you the results you want. But obviously, you know, these are things that people in all sorts of of jobs and

and positions, UH worry about. Whether it's professional recording artists, whether it's podcasters like us home podcasters you just want to record a demo. I mean, these are the sort of things you gotta think about. So thank you very much for writing in and requesting this episode, and Noel, thank you for joining me today. Usually you're on the other side of that window we were talking about. It's true, it's nice, too nice to pass through. Yeah, it's it's great to be on this side once in a while

and not stay so long that the room gets super stuffy. Uh. This, that's one of the things that this room in particular, it does get a little warm. Now we we fixed the stuff you should know podcast room because it was used to get blistering lee hot, and now it gets very cool there, and now the opposite seems to happen here. But I'm afraid to ask for anything because I don't want to end up getting Gaye force winds into the

podcast studio. But guys, if you have any suggestions for future episodes, you have anything you want to comment on for this episode, send me a message. The email address is tech stuff at how stuff works dot com, or you can drop me a line on Facebook or Twitter. The handle at both of those is text stuff H s W. And I will talk to you again really soon for more on this and thousands of other topics. Is it how stuff works dot com