Best Insulation for Soundproofing – DSP 259

This is another fantastic episode that challenges the question on its face.

Graham and Jake (still no Ashkahn, unfortunately, but he is in the intro) talk about soundproofing basics and what type of insulation is a good idea for your float rooms. As it turns out, insulation isn’t doing much of the heavy lifting though, so soundproofing probably isn’t the highest priority when selecting insulation.

Information for the Float Conference, happening this week! Tickets, Schedule, Speaker information and more available at FloatConference.com

Rockwool Roxul Safe N’ Sound 

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Transcription of this episode… (in case you prefer reading)

Graham: All right. Hello everybody, I am Graham.

Jake: And I’m Jake.

Graham: That’s right. And Ashkahn’s not with us today. He is busy getting all ready for the Float Conference, coming up August 18th and 19th. It’s gonna be the last one that we put on as Float On here in Portland.

Jake: Yeah, after that, it’s going to turn into a non-profit, which is going to be very exciting.

Graham: Yeah, so definitely, definitely make it out. It’s going to be a great party. And hopefully we get a chance to meet all you listeners in person out there. Or see you again if we’ve met before.

And in the meantime, we have some construction questions. Jake is kind of our main construction part of Float On, one of our owners. And today’s question is, “What type of insulation is best for soundproofing?”

Which is an interesting question. Again, I love the question. I think that it’s a very intelligent question to ask. I’m in no way making fun of the question. But I do think that it’s the wrong question to be asking. Mainly because insulation is not the kind of main factor in sound proofing. I guess this is a really common conception, which I almost blame musician studios for, because they have all of these kind of sound damping pads and things up around, you really think of throwing this soft sound absorptive material all around your spaces the way that sounds waves are blocked.

But the insulation that you’re putting up, or putting in between walls, or above your ceiling, all of that sort of thing actually has a lot more to do with protecting the heat, and heat transfer between the rooms than it does actually blocking the sound. And for sound the main forces that you have at work are a big heavy wall, and an air gap in between. And an insulation does serve a very important purpose in there, which I’m sure we’ll get to in a second. But it’s just to say that insulation is not going to be the bulk of what does the sound proofing. So looking at really heavy materials, looking at getting an air gap in between those materials, that’s the bulk of soundproofing.

Jake: Yeah, really, you know if we’re trying to effectively soundproof a room, or knock out noise, attenuate noise coming through walls, we’re using a variety of techniques. First off, we’re using reflection, which as you mentioned, a very, very heavy wall, a very, very dense.You know imagine yourself in a giant concrete room, and you yodel, and all of a sudden that yodeling is bouncing all around the room. Well that’s just energy coming out of my throat. And that energy is staying within my space. So that’s what the reflection is doing. It’s very heavy, it’s very hard for noise to pass through that.

Graham: So even though it gets louder within the space you’re in, there’s less sound transferring to the outside.

Jake: Exactly. Exactly. Now what do we do about energy that’s actually making it through the wall and getting in to that wall cavity? As Graham mentioned, this is where insulation does play a role in sound proofing, but not a huge role. What it’s doing is it’s absorbing noise that’s bouncing around in that space so it doesn’t just reverberate and echo around inside there. But definitely the most important thing to insulation is that thermal barrier. We use roxul-

Graham: So just to kind of paint a picture of the purpose that the insulation serves, right? So you have these two sides of a wall. You have a space in between it. And it’s kind of like you can almost picture like either a drum, or a guitar, or something like that, right? When you just strum on a string and there’s no guitar body there with this resonant space for the sound to go through, you don’t really get much noise, you know, if you just put a string on a two by four, it doesn’t make a very loud reverberation. But when you have that hollow space for the noise to echo around, that’s where you get this projection. And so if you don’t have insulation inside your walls, you’re kind of turning the entire thing into a drum head, or into a-

Jake: Kick drum. That’s what I think about, a kick drum.

Graham: Yeah a kick drum.

Jake: Like when the drummer puts a pillow inside there, dampen it out and stuff?

Graham: So and then you can imagine the same thing, if you just shove a blanket inside a kick drum or you shove blanket inside a guitar-

Jake: Pillow, yeah.

Graham: It’s once again, not going to project sound very well. So the same force is at work with insulation. You’re kind of just shoving that insulation inside the wall cavity so that you don’t get the sound waves bouncing around and actually amplifying when they’re in there.

Jake: Yeah, absolutely. So we’re looking at reflection. We got a lot of mass to keep that noise from getting in to the wall cavity. We have absorption within the wall cavity if we do have some noise bouncing around inside there. You’ll also see absorption on the surface of a really heavy wall. You know that’s where you see these acoustic panels, or something like that, where the noise is not bouncing back towards you. One of our float rooms, two of our float rooms at Float On, is porcelain tile, you know, floor to ceiling. They’re the open tanks. When you speak in there, the noise bounces around. And more importantly, when the pump kicks on, even though it’s a similar volume as our other pumps, just because those rooms are so solid, that noise is really bouncing around inside there.

But again, back to putting it on walls. Where you’ll see, like you mentioned, recording studios. You’ll see those foam all over the walls, with the little cones and spikes. And the cones and spikes are actually diffusion. They’re taking any sound waves, and any energy hitting that wall and bouncing it in many different directions, as opposed to directly back at the sound source.

And then of course, I think, what is our other sum, decoupling, you know? We’ll decouple everything we can. Like we’ll-

Graham: Yeah, but that’s that air gap in between.

Jake: Yeah, that’s that air gap in between things, so like if you’re doing a double side wall system, or even more simple, like actually isolating your tank from the floor by putting in on  a HDPE high density polyethylene platform, and then attaching vibration isolation pads, or anti-vibration pads to the bottom of that, and that’ll effectively decouple your tank from the floor as much as you can.

Graham: Yeah, given the gravity is really trying to pull it down towards the floor as best as it can.

I lost track. Did you mention damping?

Jake: I’m always losing track. No, I did not. Tell us about damping.

Graham: So damping is actually, a good example is those vibration isolation pads that you’re attaching the sound proofing platform to underneath your tank. You’re kind of creating an air gap and the only points of contact now between your tank and the ground are these vibration isolation pads, which are tiny usually like three inch by three inch squares. You can get them in different sizes. But they actually change density of material as they’re going along. So that change in density is that damping effect. Sound waves don’t like going through materials of different density. And in a sense, the decoupling is kind of just an extension of that damping. Like you’re going from solid material into air, and then back in to solid material with decoupling. So in my mind, those two are related, I know they’re totally different effects, but it’s that same ideas, you just don’t want the exact same density of the same material up against itself. And the best way to separate it is with an air gap.

Jake: Yeah, yeah. Just for one other note since you’re gonna find a lot of different AV pads, anti-vibration pads, vibration isolation pads out there. We like the rubber ones. We tend to stay away from the cork and rubber ones. The cork tends to break down over time. That magnesium sulfate, the Epsom salts getting in there will get in little crevices and then it actually blow it apart.

Graham: Which is crazy because you think of cork as being like water proof.

Jake: I know. That’s what we thought.

Graham: Salt will still destroy cork, which is crazy.

Jake: And as it destroys it, it compresses it down, so then the attenuation of sound is worse. So yeah, just staying away from that cork, for sure.

Graham: So that said, now that we’ve explained why insulation is not actually that important for sound proofing, what insulation do we like?

Jake: Well again, you know we’re not paid by any manufacturer, and there’s lot of different brands out there. We like to work with Roxul SAFE’n’SOUND. It’s a rockwool. It’s an extruded basalt. And the reason that we like to work with that, is because there’s no food for mold or mildew to grow. Like the best designed room can end up with a weak point, like what if one of your airtight junction boxes all of a sudden has a small pinhole in it, and then you get this really humid float tank room air exfiltrating into your walls. Like there is a possibility for moisture at some point, and some time, even in the best designed system.

Graham: Did you say exfiltrating?

Jake: Yeah, yeah. Like basically like, yeah. Infiltrating the wall, exfiltrating from the room. Is that right?

Graham: I’ve never heard the word exfiltrating. I hope it’s a exfiltrating.

Jake: Exfiltration? I hope it’s a word.

Graham: I’m sorry. My brain’s just like that’s an awesome one.

Our researcher says yes, in fact that is a word.

Jake: That is a word. See.

Graham: Nice, okay good one. Putting that down in little Graham book, yeah. That’s going in my Gournal.

Jake: I’ve been putting that down for years, baby.

But anyways, the reason that we like to use that extruded basalt, or like any kind of rockwool, slagwool, again, no food for mold or mildew to grow. If you have a paper faced fiberglass, the mold and the mildew will climb up the paper face. Stonewool, theoretically, once it’s dried out after it’s been wet, it gets back to the same R value that it had before. Yeah, I think that’s what we really like. Staying away from, again, the natural fibers. Any cellulose, any denim, anything like that.

Graham: Yep. And again, you know the biggest thing, like Jake was saying, find stuff that’s not going to be destroyed by moisture, and after that, find stuff that will help a little bit with maintaining temperature inside the rooms. And other than that, just the fact that you have something that is absorptive in there, that’s loose and not solid, and that’s a different density than your drywall, that’s what’s gonna do the soundproofing. It’s just gonna stop those sound waves from reverberating around inside. So don’t worry too much beyond that for exactly what type of insulation you’re getting related to soundproofing. There’s just these other factors related to insulation that are a lot more important in your choice.

Jake: Definitely. Definitely.

Graham: And if you have questions of your own that I will absolutely not make fun of when you submit them, go to floattanksolutions.com/podcast and we’ll answer them right here on this very podcast.

Jake: Right, right, right here.

Graham: Right, right here.

Jake: Right here.

Graham: And if you have any really fancy words that you’d like to include too, we’ll make sure that they’re actually true and out those on the air as well.

Jake: That could be a whole show. I like it.

Graham: No one submitted a tongue twister question either, but I think that would be hilarious if any of you feel up to the challenge.

Jake: I like it. I know where Sally sells seashells. I know where that happens.

Graham: All right, thanks everybody. We’ll talk to you tomorrow.

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