Transportable Attenuation Wall?

[SteveCallas]

I've recently left my previous 3rd floor apartment for a much larger townhouse. I've gone from having to worry about potentially moo off six neighbors to only one, and the shared wall is in the kitchen, a good distance from the HT setup - down a hall way, through the dining room, into the kitchen. When I am in the kitchen near that wall, I can occassionally hear the thud of my neighbors closing their kitchen cabinets, so the wall isn't soundproofed very well.

Since I want to enjoy this new place without having to worry as much as I did in the last, I'm thinking of building a transportable wall that I can move into place to block the hallway when I want to enjoy my system at spirited levels. I have realistic expectations and know that it won't come close to soundproofing the ht setup, however, I think I should be able to do a decent job of attenuating the sound a fair amount for the minor labor and cost of such a project. Right now I am picturing something like a sandwich with 3/4" closed cell rigid foam at the core, a layer of 1/2" OSB on each side, a layer of roofing felt on each side of that, a couple layers of heavy duty cardboard on each side of that, another layer of 1/2" OSB on each side of that, and then finish it off with poly batting and fabric or something like that.

The rigid foam insulation and cardboard layers would act merely as a "dielectric" so to speak between the layers of OSB, I know they won't really do anything on their own.

So how does this sound? Any inexpensive materials you experts are aware of that I should add to my list? I assume I should use caulk instead of screws to hold these layers together? This transportable wall won't be a flush seal with the hallway of course, there will have to be some slack inbetween - would I just be wasting my time then, or could I still expect a pretty reasonable reduction in spl? Any info is appreciated.

[bpape]

A door to the room, a second layer of drywall with Green Glue in between will to tons more than all you described above.

Bryan

[shr-t]

Going through all that trouble will have little effect if you don't seal the room, i.e. seals on the door etc. Consider sound as air pressure difference -> sealing is essential!

[bpape]

Agreed. To get the most isolation, you'll want to caulk the seams and put seals on the doors.

Bryan

[SteveCallas]

There is no door in this hallway and I can't exactly add a door to a property I am renting I can't do a second layer of drywall on the shared wall either, though I doubt that would have much effect anyway unless I did the whole kitchen.

I know a sealed solution would be best, but even when I shut a door to a room with sound originating form it, and the door has an air gap at the bottom and isn't air tight of the sides or top either, it still makes a noticable difference in attenuation. I'm envisioning something like that, except using a thick, relatively dense wall comprised of a variety of materials instead of a poorly constructed door. The opening to the hallway is a bit under 4'x8', so this wall will overlap the opening a bit.

I went searching for some materials yesterday and found some black insulation boards. It's apparently made from tar and fiberglass, and it seems to dampen sound very well based on a few knuckle knocks. 1/2" sheet was about $9. 1/2" OSB was about $7. Rigid foam sheets were quite expensive, $12+. 30lb roofing felt was about $13 for a decent sized roll. 1/4" hardboard was ridiculous at $15 a sheet. Based on this, I think I will go with 3 layers of OSB and 2 layers of black insulation board with roofing felt inbetween each layer. I will probably carpet the exterior.

Anybody wanna take a guess on what the db reduction will be?

[shr-t]

I just don't see any reason to over-engineer it.

With as little as 1% leakage your maximum potential sound isolation would be 20dB, I couldn't find a proper graph on the subject, but check out "Sound Leaks" about 3/4 down on this document. Maximum potential sound isolation is highly dependent on leakage percentage. With no sealing, you're just as well off with a single sheet of plywood of which ever thickness is strong enough to stay standing and moved around, like 3/8" or something... Well, as for bass frequencies, you might want to add more mass but anyways, a single 3/8" plywood will have an Rw value in the 30dB range.

[Wayne A. Pflughaupt]

To make sure I understand, there are no doors between the kitchen and the HT room that could be closed? Anyway you can give us a floor plan?

Regards,
Wayne

[SteveCallas]

I'll go ahead and post a couple pictures tommorrow.

Without doing any modifications to the hallway, I'm wondering if there is anyway to get this transporatble attenuation wall pretty tight up against the hallway opening to minimize leakeage. I'm thinking perhaps a border of compressible, open cell foam, and then resting something heavy against the other side of the wall to force it against the opening, creating a semi seal?

Even with leaks though, if I could attentuate the sound into the kitchen by 20db, that should be all I need. I can listen at say -28 or so with absolutely no concern or worry for even potentially bothering my neighbor now. Explosions and dynamic peaks in the -15 to -20 range probably do make their way through the kitchen wall though. An extra 20db capability would work out pretty nice, though 30db would be even better.

[SteveCallas]

The first picture is from the living room into the hallway with the kitchen in back and the second is from the hallway looking into the living room.

[bpape]

If it was me, I'd just build a couple of plugs. 2x4 framing, insulated center, 3/4" MDF on both sides. Around the perimeter, use some 3/4" weather stripping so it can be slid in and seal up relatively well. Make it in 2 pieces - top and bottom for easier moving as 1 single piece will be pretty heavy. The smaller pieces will also be easier to find a place to store when not in use.

Bryan

[Wayne A. Pflughaupt]

Brian’s plan sounds really good. The only drawback I can see is that you will probably get tired of setting it up and taking it down all the time. Is there another exit from the living room that you could use, and keep the “plug” in place all the time?

Or, maybe you could mount it to the wall, on hinges. That way you could swing it aside when you don’t need it. When you move it could all come out, with only a few holes where the screws were to spackle and paint over. No one would even know it was there.

Regards,
Wayne

[SteveCallas]

Even with 3 of my 7' Avalanche LLTs, there will be plenty of space in the living room to store these walls, so that's not a problem. The potential problem I see with using only 3/4" thick weatherstrip is that I will probably scratch up the walls pretty bad. I'd need to get something thicker. Also, if I got the bottom piece in, how would I get the top piece in if it is supposed to be air tight?

[bpape]

If you make the hard panel 3/4" narrower than the opening, then you're only compressing the stripping by 50%. That shouldn't cause more than a paint rub at the most. For the top panel, you'll just not put weather stripping on the bottom of it so it can slide in on top of the first one and compress it on top of the bottom panel and on the top of the top panel.

If you use too much stripping, you'll end up sacrificing more isolation. Thicker stripping just means compressing more thickness. To get much thicker, you'll have to go multi-layers and they'll pull apart over time.

Bryan

[SteveCallas]

Was examining the hallway last night to see if I could make this idea work - another problem is that there is molding on the bottom edges. I'm thinking again of having this wall a little larger than the opening to the hallway, putting something like weatherstripping on the perimeter of the back side of the wall, and then using something heavy to compress the wall against the opening. This would create a seal on the sides, but not the top and bottom. It would be pretty easy to set it up and take it off too.

[bpape]

Another option would be to make the face of one side larger than the opening and put stripping on the back side. That way, it would overlap the walls from the inside of the room and somewhat cover the compression gap between the panel and the hallway. Same principle as doing drywall in overlapping layers - no one straight path for sound to move through - has to make a 90 degree bend.

Bryan

[SteveCallas]

That's a good idea - I will do just that.

[terry j]

Why not knock on the neighbours door, say hi and explain the sit. Ask them if you could play a test scene, and pop over and see how it sounds next door.

For all you know they may hardly ever be in the kitchen, and have their own lounge room door or something and can hardly hear your stuff in their loungeroom/bedroom.

It will also give you a gut feel for how effective your treatments need to be, let's them know you are a courteous neighbour and may turn them around to the joys of experiencing 12 hz sounds at 110db!

[SteveCallas]

I can hear the thud of them closing their kitchen cabinets when I am in my kitchen, so I know that that wall transmits sound pretty easily. Also, sound from my equipment travels pretty easily down that hall, so I know that they would be able to hear my setup when I start approaching the levels I really want.

[SteveCallas]

Boy, a sandwich of 5/8" OSB, 30lbs roofing felt, 1/2" black insulation board, 30lbs roofing felt, and 5/8" OSB is pretty heavy Bought some heavy duty handles, now I just gotta get some carpet.