Sealing off bedroom windows acoustically

laptoppop · Post by **laptoppop** » Sat May 17, 2003 9:04 am

I've got to seal off a couple of bedroom windows acoustically. The problem is, *nothing* can show from outside the house. I need to leave the 2" wood blinds on the windows. I recognize that I'm dealing with a bad situation - just trying to do what I can.

What I'd like your opinion on is my crazy plan to reduce leakage in/out the windows. I'm thinking of taking a sheet of 1" thick plywood, putting 4 2x4 strips of lumber on their side in a big square at the edges of the plywood, then sealing everything tight. If you lay this on its front, it would be like an open box. Then I'd put rubber gasketing on the edges of the 2x4s, and 1" insulation inside the box. I'd then put the whole thing over the top of both the windows and the blinds and screw it to the wall with some brackets. From the outside, it would just look like a normal window with closed blinds.

Does this sound like I'd get some kind of attenuation this way, or am I way off base?

Thanks,
-lee-

Post by **John Sayers** » Sat May 17, 2003 10:01 am

If you want to keep the outside look that's about all you can do, but I bet steve has other ideas

- make sure you paint the plywood black so it doesn't show through the blinds.

cheers
john

knightfly · Post by **knightfly** » Sat May 17, 2003 3:06 pm

Lee, SCREW THE PLYWOOD (not TO anything, just SCREW it :=)

Seriously (I CAN occasionally do SERIOUS, really I can...) plywood is more expensive and less effective than either gypsum board (sheet rock) or MDF/particle board. The only thing plywood is better at, is bend/flex strength and lighter weight for things you need to carry.

Here is a link that may help with your problem -

http://www.johnlsayers.com/phpBB2/viewtopic.php?t=239

If you have any more questions, fire away - sometimes when I go back and read my explanations even I have questions ??!?*$*#??

If that wasn't what you were trying to do, then don't read the previous comments, and don't click on that link ...

laptoppop · Post by **laptoppop** » Sun May 18, 2003 3:17 am

I've got a problem situation -- my son has severe asthma/chemical sensitivities and my wife read an article saying MDF outgasses formaldehyde which is bad for his condition -- so thats not possible in my strange situation.

The room I'm finally actually getting is full of compromises, not the least of which is the two windows I need to try to block acoustically, but cannot have anything show from the outside -- in other words, I can't even get rid of the blasted window blinds.

I appreciate your knowledge regarding plywood versus MDF versus gypsum board. I'll admit it puzzles me a bit - I would thing 3/4" plywood would be heavier than gypsum wallboard and I would think mass is good for sound - but you're the man.

I'm also a RANK beginner at construction techniques.

Would it be better to use wallboard instead of plywood over the frame? In other words, still make a box of 2x4s put on end, but cover that with wallboard, stuff in some insulation, put gaskets on the end of the 2x4s, and screw it up to the wall.

I'm not expecting a *great* sound barrier - more like a sound attenuator. I'm just trying to figure out what I can do that is removable and would give some improvement. I wish I could put things on both sides, like the other link, but that's just not possible in my case.

So, should I replace the plywood with wallboard? How many layers?

Thanks much,
-lee-

knightfly · Post by **knightfly** » Sun May 18, 2003 10:47 am

Lee, you're right about the aldehydes in MDF and particle board outgassing - I'm not sure if you could stop that with a heavy coat of Urethane varnish or not.

In your case, it sounds like wallboard would be better - the reason I drew that plug using particle board was mainly for durability.

As near as I'm aware, an equivalent amount of weight SHOULD perform at the same or similar level, so the 1" plywood should be approximately equal to maybe 5/8" particle board -

For your particular situation, especially where you can't put a layer next to the window surface, I would make a sandwich using 5/8 sheet rock (on the frame) then a layer of 1/2" soundboard, then the heavy plywood - if you can find Rockwool locally, try and put a layer of that inside the "box", to help absorb outside sound coming thru the window glass. Keep the wide "shoulder" around the inside of the window molding, and use as wide a gasket around the inner window molding as you can.

You'll definitely want the whole thing so you can tighten it into the window as you mentioned, so you can compress the (closed cell foam) gasket by at least enough for a tight seal.

If these plugs are going to be removed from time to time, I'd be sure to get some of those heavy Stanley Barn door handles - if you can, mount them with long screws that penetrate into the frame by at least 1", and drill small enough pilot holes so the threads get a good grip.

The handles will work best, especially for something this heavy, if you can mount them at a height so that, with your hands gripping the handles and your elbows bent until your elbows touch the face of the panel below the handles, your fore-arms should be angled down and away from your body at about 15 degrees or so - this will let you use your elbows against the panel while having enough lifting power to raise the panel slightly, controlling the angle of the panel with hands and elbows while you install or remove it.

That was a pretty crappy explanation - if you don't get what I meant, say so and I'll draw a picture next time... Steve

Gearslutz.com Jules · Post by **Gearslutz.com Jules** » Wed Jun 04, 2003 8:37 pm

I had a band I was working with cut some heavy ply wood just smaller than my kitchen window surround / sill, then using a butter knife I pushed socks (clean) lenthwise into all the gaps, this held the board in place and blocked the sound out pretty well. I was able to do punk rock vocals in my apartment and one of the bands got signed to Virgin Records UK and the tracks were released....

laptoppop · Post by **laptoppop** » Sun Feb 01, 2004 1:36 am

So my original window covers have really worked out well. They knock down the sound wonderfully.

But now..... <grin>

I'm looking at a different space. (I've got this one pretty much finished, time to kill myself again!) This space has several windows, and I don't want to give up the light.

In another thread, I believe it was mentioned that glass actually has pretty good properties -- more density than wallboard.

I wonder about making a window cover, like the others, but with a glass window inset. I'd angle the glass a bit so I didn't have two equal panes of glass. I'm also thinking about making it have a number of smaller panes with wood in between so that each piece is smaller and stiffer. Around the edges inside, I'd put rigid fiberglass wrapped in cloth.

I guess what I'm thinking of building is sorta kinda like making a control room window out of normal outside facing windows.

Thoughts?

-lee-

Post by **John Sayers** » Sun Feb 01, 2004 4:22 am

I do it all the time Lee.

Here's a pic of the booth in Left Bank - it's an outside window treated like a control room window.

cheers
john

knightfly · Post by **knightfly** » Sun Feb 01, 2004 10:02 am

OK, Lee, now if you tell us you also want this window to OPEN and still have as good isolation, we WILL hafta kill ya...

Steve

laptoppop · Post by **laptoppop** » Sun Feb 01, 2004 12:27 pm

Opening.....now that sounds cool!

So - is it better to have one big window, or a set of smaller panes? I would *think* smaller panes because they would be more rigid, but sometimes acoustics get counter-inuitive.

-lee-

Post by **John Sayers** » Sun Feb 01, 2004 7:04 pm

use 1/2" or 5/8" glass and you'll be OK with one sheet.

cheers
john

knightfly · Post by **knightfly** » Tue Feb 03, 2004 9:51 pm

If the Insulco "freebie" calc is right, smaller panes but everything else the same= same STC but better TL at lower freqs by several dB. I think though, that to accomplish that you would just have to use a smaller window unless you planned on building frames as stiff as your walls -

Never seen a studio with "french windows"...

Willangus · Post by **Willangus** » Mon May 17, 2004 1:12 am

Hey guys,

I tried to check out the plans/drawings, but it appears this link is broken. Any updated link? As a fellow rank beginner, I need all the help I can get.

Also, any idea of what the attenuation of this box is? I probably would build it with MDF (or whatever the most isolative material would be).

Thanks!
-Will

knightfly · Post by **knightfly** » Mon May 17, 2004 8:03 am

Sorry, Will - we changed servers a while back and I've still not caught enough time to fix all the links - here's yours -

http://www.johnlsayers.com/phpBB2/viewtopic.php?t=239

If you find any more, call it to our attention - if you're desperate, just replace this

http://www.homer.com.au/phpBB2/

with this

http://www.johnlsayers.com/phpBB2/

then paste in the rest of the old link behind the end slash, and it should work... Steve

(I fixed that link if you don't want to cut and paste...)

Willangus · Post by **Willangus** » Wed May 19, 2004 1:34 am

awesome--thanks, knightfly!