Soundproofing Rehearsal Space on the Cheap

So the college band have gone our separate ways with plans to correspond and live dirt cheap for two years while we save money to make the big push. I find myself living in an apartment with so-so soundproofing (I'm aware that the neighbor's TV is on when I'm quiet, but not what's being said on the TV) and a need to make enough noise with my voice (and accoustic guitar and a keyboard, think 85dB or so) to compose and record stuff to send to the others. I'm in the corner on the first floor of a two-story building. After making some simple removable sound plugs for a set of sliding windows and a vent that opens into the other room (the one with jalousie windows!) I'm in a position where I'm concerned primarily with the neighbor directly above me and secondarily with one to the side who is separated from me by an additional closet. Goal: To have 85dB in my room sound to them like their 65 dB TV sounds to me now. Constraints: -The place is rented, so any construction I do must be free-standing and able to be dismantled by myself. -Budget. If am unable to sing as loudly as I need to I will be increasingly willing to spend more. I'm working for a consulting firm and making pretty good money, but am currently swamped with startup costs. In the nearterm, something like $500 -Space. I need my sound isolation space to be big enough to support me and a guitar or me and a keyboard. My room can fit a 5'x7'x7' enclosure. My first thought was a 2x4 skeleton (5'x7'x7' exterior) with double layered 3/4" MDF on all sides and floated on 2x4's. A single layer of MDF at local home depot prices is $420 or so, meaning the entire project probably runs $1200. I want to understand my options and outcomes better before spending that kind of money. So help me think through this. Given I'm primarily concerned with the neighbor upstairs could I get away with a 4 walled structure+ ceiling with no floor? Could I throw up a bunch of drywall sheets for the surfaces instead of the MDF (Total price ~300)? Given that this is landlord's carpeting underneath is the extra mess of drywall more than it's worth? I'm willing to try cheaper/less effective solutions first if I have a more expensive backup in case it's a no go on the front of disturbing neighbors.

Hi there "mosa". Welcome! :) It sounds like what you need basically is an isolation booth big enough to fit you and your guitar in, and with isolation on the order of 40 dB or so. You clearly already have the basic idea on how to do this, from what you say, but there are other issues that you it seems you haven't considered yet. The first is weight: to isolate sound you need mass, and lots of it. Yes, 3/4" MDF is one option, and yes 5/8" drywall is another, but they are both heavy, and indeed they MST be heavy in order to isolate. When you say you are on the first floor of the building, that can be confusing in some countries, so I'd like to clarify that: In some places, "first floor" means the one sitting on the ground, while in other places "first floor" means the next one up, since the one on the ground is called the "ground floor". Since you are in the USA, I'm assuming that "first floor" means the one sitting on the ground, and hopefully that the floor under you is a concrete slab poured directly on Mother Earth, with no other rooms below you. Please say Yes! :) If that's the case you are probably OK, but if your floor is actually just wood supported on joists, and there is something below you, then there might be an issue: the structure might not be able to safely carry the amount of extra mass you need. So it's rather important to confirm that! Second is ventilation: You are basically planning to build a closet where you'll be singing and playing hard, working up a sweat, and breathing. In order that you can keep on breathing after a few minutes, you absolutely need some type of ventilation system to feed you clean air and exhaust the stale air. Either that, or you have to figure out how to sing without breathing... :) The ventilation system doesn't have to be complicated, but it does have to isolate enough. You can't just chop a hole in the wall of your booth, as that would defeat the entire purpose of the booth, and wouldn't work anyway: you need a small silent fan to move air through the booth, and you need a simple basic silencer box to keep the sound contained. Third is the door: it has to be just as massive as the walls, and it has to seal absolutely air tight, and there can be no penetrations through it, such as for the lock set. That complicates things a bit, so it's something that you do need to consider. Forth is light: I'm pretty sure you don't like singing and playing in pitch blackness, so you need either a window, or you need electrical power. Either one complicates things a bit more. Probably electrical power is the least expensive of the two, but it needs to be done safely and without compromising your isolation. So those things that are rather important, and often overlooked in the type of project you are planning. OK, back to the basic issue: how to isolate. Your basic plan is fine, but is only half of the solution. MDF has a density of around 800 kg/m3, so the surface density of 1.5" of MDF is roughly 30 kg/m2, or 6 PSF. According to mass law, theoretically you'd be getting about 34 dB of isolation from that, but call it about 30 to be realistic. The good news is that that might actually be enough for what you want. The other good news is that if it isn't enough, you can always add resilient channel to the inside of your booth and put a layer of 5/8" drywall on that, which will greatly increase your isolation. The bad news is that it breaks your budget! Yes you can substitute 5/8" drywall instead of 3/4" MDF, but then your theoretical isolation drops to about 30 dB, but call it more like 25 to be realistic. Not good enough. The other issue is structural integrity: MDF will provide that for your booth, drywall will not. But there's an alternative: Make the first layer 3/4" MDF, and the second layer 5/8" drywall. The MDF gives you the strength (and the cost!), then the drywall adds useful extra mass (at less cost). You'd be back up around 30-something dB of isolation, in theory. By the way, your singing plus guitar is probably closer to 100 dB than 85... So getting that down to 65 needs about 35 dB of isolation. But 65 is still pretty loud: that roughly the level of normal conversation. Anyway, having said all that, I suspect that you'll have enough isolation with the MDF + 5/8" drywall plan, even though this is just a single leaf solution, and if you find it isn't enough, then your "Plan B" is still available: Resilient Channel plus drywall on the inside of the booth. That makes it a full 2-leaf system, which isolates much better. For your final question, to protect the landlord's carpet I would use a sheet of plywood or OSB as the base for the entire booth, and build on top of that. One more thing: it will sound really awful in there! You WILL need to add some acoustic treatment as well, probably in the form of ordinary wall insulation, so you need to budget for that too. Hope that helps! - Stuart -

Thanks for the prompt response! Yes, I am on the ground floor, so I'm not overly concerned about large point loads. I was imagining that if I could do it for $500 I would be willing to deal with a lack of ventilation and work for 15 min at a time with fan breaks. Anyways, I think you've convinced me that I need to do it right if I do it at all or I'll probably end up with less than 25dB. I'm going back to research but I hope I can appeal to your knowledge again by adding to this thread in the future.

hope I can appeal to your knowledge again by adding to this thread in the future.

You sure can! That's what this place is for. By the way, there are a few threads on the forum about vocal booths of various types: it might be worth looking over those. The "search" feature here isn't terribly powerful, but it can get you close... - Stuart -

So let me clarify with a schematic image showing the walls from an overhead view. The entire image represents the 5'7' footprint of the booth and before shrinking from 840px wide to 700 it was 10 pixels to the inch. I build my two 5'x7' walls from 2x4's like you would do for a regular interior wall, but I screw a layer of 3/4" MDF on the outside before adding the 5/8" drywall. I then build the longer walls and screw from the inside of these walls at the corner to join with the shorter walls. Then I add 2x4's every 16" along the floor to support a layer of 3/4" plywood followed by 3/4" MDF. The ceiling is identical to the floor and is placed on top after adding more 2x4 crosspieces to match the floor. Is this making sense? 4.5 psf was the best I could find for a pre-hung door. I think were I to go with a slab I'd end up with a worse outcome just due to the added difficulty of lining it up perfectly. Given that I have only the 4.5psf here what are the implications for the transmission of my booth as a whole? I haven't yet researched ventilation systems. Is the 10.7" on my front wall going to be sufficient for a home-made system? edit* The front wall is of course not supposed to extend in front of the door... -_-

After a bit more reading I've decided that a 2x6 stagger stud setup is going to be the way to go. See the new image. I'm eager to cut some of the studs now when I have time to work at a friend's machine shop. Do you think leaving 12" is sufficient to add ventilation? Can someone who's built a ventilation system for an iso booth tell me whether what this guy did is a good plan? I'm a little skeptical that a 4" PVC with two elbows is equivalent to the STC I'm going to have for the rest of the booth. I really appreciate any feedback here.

I've decided that a 2x6 stagger stud setup is going to be the way to go.

Ummmm..... Why? You are not planning to have an inner-leaf, so there's no purpose for the second layer of studs. And if you DO need an inner leaf, then RC plus a single layer of drywall will actually give you pretty much the same isolation as staggered studs plus a single layer of drywall, but without the lost space. I'm not understanding the reason for those staggered studs. I'm also not understanding why you want to switch to 2x6 studs, when 2x4 are already more than enough. This is not a structural booth that has to hold up another floor above it! So why 2x6? Single studs would be fine, and 2x4 would also be fine. - Stuart -

Soundman2020 wrote:

I'm also not understanding why you want to switch to 2x6 studs, when 2x4 are already more than enough. This is not a structural booth that has to hold up another floor above it! So why 2x6? - Stuart -

So I had two reasons for not looking into channels 1. I couldn't find a retailer who would sell me less than a 8ft 24-pack for $200. I need about half that for the interior layer of drywall, and simply changing the size of my floor and ceiling supports (4*4'5"+4*7' = 50 ft) from 2x4 to 2x6 is considerably less. I think I must have miss-communicated. The studs aren't 2x6. only the rectangular base on the floor and ceiling. 2. I spoke to my uncle (a general residential contractor) who told me in his experience that the staggered stud walls (we're talking only drywall, here) did better at blocking vocal frequencies than 2x4 framed walls with channels. That said, yes, I am adding a second layer of drywall on the interior because it's cheap to do. With some rearranging of the room I was able to increase the planned width of the booth by 4" and I'm less concerned about running out of space even if I decide I need two and a half inches of treatment on each wall. I'm obviously out of my depth here, so if it still seems like I'm talking crazy to you, maybe I need to back up.

1. I couldn't find a retailer who would sell me less than a 8ft 24-pack for $200. I need about half that for the interior layer of drywall, and simply changing the size of my floor and ceiling supports (4*4'5"+4*7' = 50 ft) from 2x4 to 2x6 is considerably less. I think I must have miss-communicated. The studs aren't 2x6. only the rectangular base on the floor and ceiling.

There's an alternative to RC: You can use plain old ordinary hat channel too, but mounted on RSIC clips, or Whisper Clips, or something similar. You can buy as many or as few of those as you need.

simply changing the size of my floor and ceiling supports (4*4'5"+4*7' = 50 ft) from 2x4 to 2x6 is considerably less.

Yes, but you need a larger number of studs! Assuming you were going with 16OC, you can't just split every second one to the other side, as that would give you 32OC, which is no use... At very best you need 24OC on each side, which is the same as 12OC for a single stud wall... so you are using 50% more studs, as well as more nails, more caulk...

told me in his experience that the staggered stud walls (we're talking only drywall, here) did better at blocking vocal frequencies than 2x4 framed walls with channels.

Resilient channel or hat channel alone? I agree that hat channel by itself would be no use at all, since it has no acoustical isolation properties (even though it looks very similar to resilient channel), but proper RC, or hat channel on clips, is better for mids. Take a look at IR-761. http://archive.nrc-cnrc.gc.ca/obj/irc/d ... /ir761.pdf This is the graph for 2x4 studs (24" OC), with a single layer of 5/8" drywall on each side, using resilient channel on one of those (page 183): And here's the graph for 2x4 studs, staggered (24" OC), with a single layer of 5/8" drywall on each side (page 281): The RC wall does much better in the mids, which is vocal frequencies (but not so well for lows). Even the STC rating for the RC wall is better. I suspect your uncle was confusing RC for hat channel. It's not the same at all, acoustically.

With some rearranging of the room I was able to increase the planned width of the booth by 4"

Great! Every inch counts. More space is better.

even if I decide I need two and a half inches of treatment on each wall.

You almost certainly will: it's a very small booth, so usually the only way to make that sound reasonable is to make it pretty dead.

so if I'm still sounding like a fool to you,

Not at all! The only "fool" is the one who DOESN'T ask questions! Acoustics is a huge subject, and it take a while to get your head around the basics, then an even longer while to get your head around the more advanced stuff. It seems to me, the more I learn, the longer that "while" seems to get! It's like running in a nightmare, where no matter how fast you run towards the exit, it seems to get further and further away, not closer.... :) So I get exactly where you are coming from! What looks intuitive and obvious about acoustics at first glance, actually isn't so clear, once you get into the details... - Stuart -