About the innerwall soundproofing/acoustics. John? Anyone?

[Tomi M.]

Cheers everyone!

This picture shows John's (?) idea of saving some space: http://www.saecollege.de/reference_material/images/My Wall 2.gif , what is the STC figure of this construction? Would it be a lot better if constructed using 2 walls using resilient channel or staggered studs construction? I need pretty good STC. I'm building my studio/live room mainly for band rehearsal place (the studio side is an added bonus ). I need to use as little space for walls, floor and ceiling as possible as the space is limited. I think the size of the house is about 6 m wide, 14 m long and at the moment 2,20 m high. I checked the ceiling joists and seems it would be possible to heighten them adding new joists above the old ones and cutting the old joists off. This would add at least 0,20 m to the height... little but still more.

About John's room: I thought of putting at least 2 plaster sheets (of differrent thickness), maybe with plywood in the middle. Which kind of plywood is recommended? And is the 50mm insulation made with fibreglass? Could that 75mm insulation be rockwool or what is that recommended Polyester insulation?

As the live room will be mainly for band rehearsing, which kinds of acoustical treatment I should consider? I though of making one wall as non-parallel wall made to work as a slat resonator. Maybe putting basstraps to other corners. What else I should consider? I might get acoustical sheets (fabric covered rigid wool?), are those good for the ceiling? Let me know what you think. And sorry I can't yet give you any accurate measurements of the room I have, but it will be about 6x10x2.5m (w:l:h)...

Thanks in advance!



t0mi

 

[Tomi M.]

bumb

Well, I'd appreciate if someone could give me some ideas/answer about the above...




tomi

 

[Alex W]

Tomi,

I'll give it crack, maybe others will pile in.

John's inside-out wall construction is a good space saver. STC rating is shown on the charts on his site. This works best for room-inside-a-room construction, where you'r butting it up against an existing wall. That way you get the added benefit of an air space between the two walls. A buddy of mine is using this method in his existing garage--should be complete and jam-ready in a couple of weeks so I can let you know how it all turned out. His walls are timber framed with a layer of soundboard attached to resilient channel followed by a layer of 5/8-in sheet rock.

If you're building a new structure or going for single wall construction, then the resilient channel and multiple layer approach is good. From my understanding, when layering, the important things are mass, thickness, and material density. You want the mass for sure to stop low freqencies. Changing thicknesses impedes the transfer of sound waves. Ditto a change in material provided the mass is still there. In terms of sandwiching a layer of plywood in your walls--I'd go at least 1/2-in (12.5 mm?), but it might be more affordable just to keep it all sheet rock of varying thicknesses.

I think most of John's wall designs are based on using rock wool (mineral wool) insulation in the wall cavities, rather than fiberglass.

Acoustical treatment of the finished walls and ceiling is a whole different can of worms. Do a search in this forum and you should have plenty to go on. It all boils down to eliminating standing waves and reflected frequencies. Typical acoustic treatments can handle diffusion and absorption of high freqencies, but allow bass frequencies of 100 - 600 Hz to bounce around and cause problems. For these you need to construct sealed resonant and absorptive panels where the insulation is lifted a certain distance off the wall.

I think I hit most of your points, but it was a long post. I know you're excited and have a million questions, but try and focus your posts a little more in the future on one or two issues and you might get a better response.

Happy building!

Alex

 

[John Sayers]

Yeah - Alex has pretty well covered it all.
Two points - fibreboard would be better than plywood - 1/2" in a sandwich system.
Resilient channel only works where both sides of a frame are sheeted.

cheers
John

 

[Tomi M.]

Cheers dudes!

Yeah, I kinda rambled on on that above post... I've read lots and lots (not enough though) about acoustics and soundproofing and been here for a while...

Yeah, I've been thinking about using that John's space saving construction. I just thought that is it enough to block the sound of a full rock/heavy band? I guess it's ok, if 2 plaster sheet layers (different thicknesses) and fibrewood in between is used.

I'm asking so many things so that I could avoid taking the wrong path somewhere and totally f**k up my construction.

Ceiling question: I've seen in many constructions that the ceiling is made in A-shape (ok, my english is improper here, hope you'll get it), how about if the whole ceiling is slanting? That should take some reflections away, right? The building where I'm constructing the studio has this construction that other side of the building is higher than the other.

Thanks again.



tomi

 

[Alex W]

Any kind of slanting is good. To insure against the development of standing waves, I've seen it posted that you need at least a 12 degree slope.

Alex

 

[Tomi M.]

So Alex, how did your friend's place turn out to be?

My project is still pending due to the financial situation... Hopefully I'll be able to start the work soon.

 

[Alex W]

His room turned out pretty good.

It's basically built inside about 2/3 of a standard 20' x 20' garage.

If you can envision it -- two of the walls have a large air space--one to the west where the garage door is; and one to the south where he's left space for his washer and dryer as well as an access cooridor. For the other two walls--one abuts his house (it's an attached garage) on the east side; and on the north side, the new walls abut an outside facing wall of the garage that basically runs parallel with the walkway up to his front door.

Initial testing has shown that all of the walls are providing good isolation except on the north side. We're still trying to track down why that particular area is leaking more than the others, but in the meantime he's gotten to be good friends with his neighbor on that side so it may not be that big of a deal. On that side, he's added two more layers of sheetrock to the exposed timbers on the inside of the wall without much improvement.

My only thought on this is that we abutted the new wall very close to that north wall of his garage in an attempt to maximize the amount of space available. The air gap is no more than 1-inch and maybe even a little bit less. As I continue to read and learn about all of this stuff, my current thought is that there may not be a sufficient enough gap there to really decouble the two walls--essentially the air can act as a spring/mechanical coupling. If anyone else has had a similar experience I'd be interested in hearing about it.

Regards, Alex