Acoustical Treatments Master Thread - Page 222

I've been waiting for this topic to blow up for ages. Great info SMB and Dennis.

Surely Ethan's charts make some sort of an arugment for them?

How can the change be accounted for if the science behind what Dennis is saying is correct? there must be a middle ground that involves math beyond my capability?

Say I make an ottoman and put it between the seating position and the screen (about 3-4-5ft off the front wall, that would work as velocity absorber yes? that would work? I'd planned on filling it full with 703 equivalent polyester and covering in fabric.

Not sure if:
- increasing density from outside in would help?
- plutting a plastic membrane around it and then a bit more insulation (making is a pressure absorber) would help?
- having a free air space under it i.e. Have the bottom not solid and put it on little legs? (it'll have a solid top)
- Edit: what about a ring of peboard around it?

I did that with OC705 in a pillow-top, open bottom ottoman (no membranes but with ball casters) and it was fairly effective.

I was working on our master bath remodel last weekend, prepping for tile with Cement board and that got me thinking about my theater room.

I have had a long standing problem in my theater room with 1 live wall (7.5 x 13 ft) consisting of simply studs, 3 1/2" fluffy, and 1/2" sheetrock.
Listening to the Eagles 'Hell freezes over' last night I finally cracked a joint in the wall and drew comments from the spouse upstairs, so I guess I better get on it.
So...This winters project will be to address this wall and install 9" fluffy in the ceiling joists above the tiles.


Would there be a advantage / disadvantage be using 1/2" cement board vs. 5/8" drywall on the back of the wall? Mass (psf) looks like they are pretty close to the same.

So what type of trapping would I need to do for B-D?

Thank you in advance.

Empirical evidence trumps theory every time. I'm not much of a math guy, but I know how to measure.


The best places for bass traps are straddling corners, and flat on the front and rear walls with an air space. Absorbers out in the middle of the room will not do nearly as much. The difference in effectiveness for the same bass trap in both places is literally three to one or even greater.

--Ethan

Hi Guys,

I need some advice on where to place some panels.

I have 8 panels in my room currently. 3 up each side wall and two on the front wall. I have two extras that are basically doing nothing in my closet and I'm considering them on the ceiling.Would you guys reccomend hanging them so they run width across, or so they run front to back?

I've seen people do both.

Does it really matter that much? ;-)

The two main places for absorbing panels is in corners for bass trapping, and at specific first reflection points. More here:

Acoustic Basics

--Ethan

That's very informative and helpful Ethan, thank you.

Specifically though, does exact orientation of say a 2 x 4 panel matter for ceiling mounting or would results from both be fairly negligable?

The "best" bass trap placement depends on what frequencies end up in what parts of the room. My approach is to have traps cover as much total corner surface as possible, including wall-ceiling and wall-floor corners when possible. Another method that's a bit more intelligent is to use bassy pink noise to find where bass builds up the most:

Pink noise aids placing bass traps

Wherever the bass is strongest is the best place for traps.

Reflection points are very specific places, so there's not much leeway there.

--Ethan

The wife and I are currently shopping for a contractor to build a 12x10 dedicated theater room. One concern for me is outside noise. I'd like the room dead quiet from outside noise, but considering our budget, I know that will not happen. I have read about adding another layer of sheetrock to help with sound. Any other inexpensive techniques worth mentioning or specific materials to use?

Soundproofing and acoustic treatment are two different matters (except for one relating point which i wont go into)

Have a read of www.soundproofingcompany.com under their articles sections.

The first thing you need to do is isolate the room. Either using double studd walls, staggered studds or isolation clips

Then if you add mass and dampening you'll be there. The door is critical, as it any other "hole" including HVAC, electrical fittings (lights, points, switches etc)

But isolation is key - along with removing all holes - think fish tank full of water, any little opening sound will find its way out.

Well, I wish it were that easy. Believe me, I know first hand. Every room is different, and I have had the whip cracked over my head from you know who many times to prove it.

You are certainly headed in the right direction. The wrong direction is trying to keep all the sound in.

Another layer of drywall won't do much. But put a layer of Green Glue between them and it'll do a lot. You have to be careful to box in receptacles, switches, etc. or the sound will go through those too.

.....yeha yeah I know. But my response was as broad as the question....

Edit: he's gotta start somewhere

OP - if you want this done right, I mean really right. Engage SMB or Dennis Erskine to advise

Thanks for the advice everyone. I'm weighing my options at the moment which frankly are a bit limited, but I at least wanted to try and put some effort into noise control. I won't be able to spend much, but its certainly better than nothing.

I understand room treatments and soundproofing are 2 different things. Fortunately, the wife is on board with room treatments thanks to the opportunity she sees in it as room decor.

If you could only do 1 or 2 inexpensive things on either the walls, ceiling, or floor to dampen outside noise what would you do?

How is the room situated relative to the rest of the house? Are there rooms above? below? only to the side? For example my theater has nothing above or below and one exterior wall, so I'd treat the 3 interior walls only.

Its in the corner of the house, in the basement with 2 exterior walls facing south and east. It has rooms facing it along 2 walls, north and west, and a room above it.

Are the exterior walls for the room above ground or below ground?

CJ

The house is a split level, if you can picture those basements....half of it is below ground, the other half is above ground.

Just a quick post to let people know that if they are looking for oc703 (owen's corning 703) in Atlantic Canada, here's where I am buying mine. Took me several hours to
find the place, mostly thanks to a very helpful guy at Kent's building supplies who
placed a bunch of phone calls for me. They stock oc703 2" unfaced, I think it was
around 88 cents per sqft. I'll be building my acoustic panels in a few weeks.

General Insulation
120 Troop Avenue
Dartmouth, NS B3B 1Z1
(902) 468-5232

Quick question...does this work? Seems different from all other bass traps.

http://www.diy-home-theater-design.c...rap-build.html

^^^ No, that doesn't work. Not even a little. That page is the laughing stock of people knowledgeable about acoustics.

--Ethan

Hi Ramzy

I see you say outside noise, is this noise from outside the house or all noise outside the room?

Go down to your basement for a while and sit in the general location you are planning on having your theater, listen to what noises you hear, how loud are they? Have you wife walk around normally in the room above, have her move a chair if the room above has any. Have someone flush the toilet, operate faucets etc, do these create significant noise in your proposed theater area?

This is the best way to identify what the main sources of noise are without paying an engineer to come out and assess the situation for you, it could be that you're more sensitive to the neighbors dog barking, than say, footfall from the room above.

If you want to get the most bang for your buck (or least bang, in your case) you'll be better off using your ears to start with, determining the problem sources and going from there.

Also, take some pics - post em. The more details we have, the better.

Cheers

Andrew

Well, at least he isn't recommending that one fill it with sand!

That "bass trap" is indeed just an empty cardboard tube filled with sand.

--Ethan

They should use BS as they seem to have a large supply of it.

Whooops. I recalled that he did but when I scanned it yesterday, I somehow missed that dirty word. Mebbe he should publish a tweak where he replaces the sand with mineral wool.

I have some areas where normal size base traps would be too big. However, I could make some bass traps that would be more in the 12 x 12 size for a few spots like under a 3rd row bar....would this be of any help or are they too small to do much