What's the best way to soundproof a room?

What’s the best/cheap material to soundproof a
room in a basement?
The room will be used for band rehearsals.
Loud, very loud…

If you wanna do it on the cheap, stuff the window wells with “pink” insulation and cover them with cardboard.

Then, hit the dumpster at you’re local nursing home, and collect as many of those eggshell-foam mattress thingies that you can. Hose them down with detergent to get some of the crap, piss, and blood off of em, then hang them on the walls.


Old carpet usually works the best. Happy Jamming!

have them jam, somewhere else. :wink:

I think you got some good advise here.

also close and soundproof any vents for a/c or forces air heat

Egg cartons. Lots of 'em.

Only if you are suicidal. Egg cartons will deaden a room, but they will also go up flames way to easily. Anything you use you should test to see how flammable it is. When I built my vocal boot in my studio, I lined the walls with sheets of pink fiberglass insulation. You put the paper side towards the wall, the itchy fiberglass side out. Then you cover the fiberglass with a thin cloth of some sort(preferably non flamable), and it will both deaden, and soundproff pretty well. Carpet will work, but hang it out a few inches from the wall, so there is a dead air space behind it.

Band rehearsals. Uh-huh. Sure. Nice story.

You’ve gotten some fair advice, but wouldn’t a good ball gag be a lot easier?

Egg cartons are almost useless. Insulation will help, but not as much as you’d think.

It really matters what kind of sound you are trying to eliminate. If it’s high frequency sound, then the carpet will help somewhat, and the insulation will help somewhat. But if it’s low frequency sound (kick drum, bass guitar, etc), then there’s no cheap way to get rid of it. The only way to get rid of bass is to mechanically de-couple the room from other rooms. The other way to get rid of bass is with mass - using two layers of thick drywall on all walls and ceiling will be a big help.

Another sound-deadening product is called Resilient Channel. These are metal strips that flex. To use it, you tear the drywall off your walls, screw the resilient channel to the studs, and then screw new drywall to that. Now when the drywall vibrates from the bass, the resilient channel absorbs the vibration and prevents it from being transferred to the studs, and from there to the drywall on the other side of the wall. You could also leave the current drywall up, and screw RC to that and add a second layer. But then you wouldn’t be able to get the insulation into the walls.

Without Resilient channel, the wall acts as a big speaker. Sound waves hit one side, cause the wall to vibrate, and that vibration is carried through the studs to the other wall, which vibrates in sync and reproduces the sound.

Sound transmission is rated in STC units. A typically frame room with a hollow door and one layer of drywall on the walls has an STC rating of around 33. That means normal conversation can be heard on the other side of the wall, although muffled.

Adding insulation alone (and we’re talking about something like fiberglass ‘pink’ acoustical insulation in 4" thick batts) will only increase STC by a few units, perhaps to 36 or 38 or so, and only in the higher frequencies.

However, if you use two layers of drywall, WITH the fiberglass insulation and resilient channel, the STC of the wall will go way up to maybe 55 or so. At that rating, shouting at the top of your lungs will only be heard as a quiet, muffled sound on the other side of the wall.

The most effective technique of all is to build a ‘room within a room’, and this is what recording studios do. That means framing in new walls and a new ceiling INSIDE the current room. Hang new ceiling joists between the old ones, attached only to the new walls below. Fill the new and old walls with fiberglass insulation, add two layers of drywall to the new wall, use a solid-core interior door with weatherstripping, and frame in the old window (if the local building code will allow it) and build the new wall right over it. If the room isn’t in the basement, you’d even build a new subfoor and put it on shock absorbers to prevent transmitting sound down below.

One slightly cheaper way than build a wall within a wall is to build a wall with staggered studs - use a 2x6 for the sole plate and header plate, and then use 2x4 studs, staggered so that one stud is at the front of the plate, and the next one is at the back. This means that the drywall screwed to the outside studs has no physical coupling to the drywall screwed onto the inside studs. Fill the space with fiberglass, and double layers of drywall as before.

As you can see, none of this is particularly easy or cheap. So if you can’t afford this, your best bang-for-the-buck is to go after specific weak points and try to improve them a bit. If you’ve got a door going into the room, put some thick weatherstripping at the bottom. If your problem is neighbors complaining, build a soundproof box and mount it in your window well, since the window is the worst offender for letting out sound (to build a soundproof box, frame in a box the size of the window well (or if the window is flush, a few inches bigger than the window). Fill the framed box with insulation, and put 1" plywood or OSB or drywall around it, with 1/2" soundboard under that, to make a heavy, bass-deading surface. The put a rubber seal wherever it attaches to the wall or inside the window box. If it’s going around the window, you’ll need to get some angle brackets to screw it to the wall.

If you have HVAC ducting running across the ceiling, you can get a special sound-deading material to spray on the outside, or inserts to go inside the ducts to prevent them from carrying sound throughout the house.

How effective all this is depends on the room. If you’ve already got pretty good wall construction, you might be leaking a lot of your sound through a few problem areas. But you’ll rapidly reach a point of diminishing returns. You can replace a cheap interior door with a solid one, or hang some really heavy carpet and underlay on it to try and de-couple the sound. But at some point, the walls themselves will be the problem, and then you’re cooked unless you’re ready to do some serious work.

If the basement you are practicing in is unfinished, then you’ve got almost no sound deading to the upstairs at all. Open joists, with maybe a 1/2" OSB subfloor between you and the people upstairs. In this case, get your buddies together, and build yourself a practice room. Get your parents involved to specify the size of room they want, then frame it and drywall it yourself. It’s surprisingly easy and cheap (the hard part is the finish, and you don’t need to do that for a practice room). So frame a room, fill the wall with fiberglass insulation, and put up two layers of drywall, making sure you stagger the seams. If the room won’t be used for Hi-fi listening, use RC channel on the framing before you put up the drywall. Make sure you either put up a floating ceiling, or put up two layers of drywall on the ceiling too.

Now, the other part of the equation is the sound INSIDE the room. If you’re playing or recording music, this is just as important as how much sound escapes. And THAT is what those egg-crate type things are that you see in sound studios - they are sound diffusers, designed to break up echoes inside the room for better sound. (and BTW, egg crates themselves are almost useless for this, as thin cardboard is close to being acoustically transparent. The ones you see in recording studios are made of very high density foam or plaster or something like that).

The key measurement for fixing the acoustics in the room is RT/60, or reverb time. If the room is too ‘bright’ or has slap-echoes, your RT/60 is too high. The way to deal with that cheaply is to do what was suggested before, and hang carpets on walls, break up long flat surfaces like walls by putting in columns (or bookcases, etc). The back wall should be treated with carpet and underlay or something similar.

If this room is still used as a living space, you have to be more creative. Bookcases work great in rooms like this - books are heavy and absorb sound well. Filling a bookcase with books of random sizes make a great diffuser too.

The next problem you’ll have is equalization. Every room shape treats sounds of different frequencies differently. That means that from any given sitting position some sounds in the spectrum will be amplified, and others will be cancelled. Square rooms are the worst for creating standing waves and other odd acoustic effects. Rectangular rooms are better.

I’m in the process of designing and building a home theater, which is why I happen to know quite a bit about this subject. The room will be THX certified, which means the soundtrack has to be played at ‘THX Reference’ levels. That’s bloody loud. So the room has to be acoustically isolated. I’m doing the double drywall with insulation, but no Resilient Channel, because it’s not what you want in a theater (resilient channel walls act like bass traps and muffle the bass INSIDE the room. In a theater or hi-fi listening room, you want the bass crisp and natural).

The way you design such a room is to start with your max dimensions, then do a whack of calculations on various room modes to figure out the best dimensions closest to that. Then you frame and build the room. Then, you put 16 oz batting on the lower half of the walls, and cover it with decorative fabric. Put a few columns on the walls to break up echoes, and to hide the surround speakers. This room will have a front projector and a 10’ wide screen, with speakers on each side. The seating area has to be about one and a half to two screen heights back from the screen, so it’ll be about 12’ back, with a second row on a riser behind that.

Once the room is built, then the THX consultants come in and ‘certify’ the room. This means setting the timings on all the channels (all THX amps can do that), and possibly using an active equalizer to flatten out the frequency response in the listening area. That can also be done by placing acoustic elements in the room (hanging a soft painting at the back, etc.). It’s a ton of work, and bloody expensive, but when you’re done you have a theater that provides a better picture and sound than your local multiplex.

If you have any other questions about acoustics, fire away.

I forgot another possible ‘cheap fix’. Dow and Owens-corning make acoustical caulking for sealing gaps. If the basement room you’re in now has a lot of gaps into other rooms (like spaces around HVAC ducting coming through the walls, etc) fill them with acoustic caulking.

Take your electrical plates off, and fill the gap between the electrical box and the wall with acoustic caulking. Do the same with any other gaps you can see. Sometimes electricians will mount electrical boxes back to back on each side of the wall to save time and wire, and these act like an acoustic ‘hole’ right through the wall. If you’re not using that electrical box, cover them over with a homemade dense box of some sort.

If the ceiling is unfinished, a temporary ceiling will help if you don’t want to do with a full-fledged drywall ceiling. Fill the ceiling space with insulation, and then nail up some acoustic soundboard. This won’t get rid of much bass, but it should do a pretty good job on keep your wailing electric guitar solos from making your parent’s ears bleed.

If you would pardon an old fogey’s brief hijack:

Also invest in some industrial earplugs. Not only will it protect some of your hearing, you may screen out a lot of the fuzz and tell you whether or not you’re playing the right chords.

I used to wear them under my hair when I was clubbin’ and not only could I understand what they were playing, I could also understand conversations at the bar. The rubber plug types are just a couple bucks and well worth it.

Playing loud is cool – it’s better than sex and lasts longer – but learning to read lips is not.

Thanks Sam and the rest of you guys with REAL answers.

It was just what I needed to know.

Neighbors had started calling the police due to the noise.

The basement is unfinished but they will probably finish it as suggested and continue with the room within a room.
The internal sound we hadnt even considered yet. duh…
but will now…
and you can bet they will have plenty of industrial strength
earplugs, #1 priority.