DESIGN HELP NEEDED for Sound blocking AND bass trap acoustic panel

**goonstopher** · **10-28-09, 01:53 AM**

I have finally come up with some ideas to treat a large door for sound proofing and acoustic reflections by creating custom 2 sided acoustic panels for the dual purpose.

The each door is about 80 x 30 and there are two connected doors.

I cant treat the entire area for practical reasons so taking out for the door knob I have 24 x 40 to work with on the top and 24 x 30 to work with on the bottom of each door.

On the internal side both will have 4" of extra dense rock wool with fabric stapled to a plywood backing. The sound blocking/mass loading back side is where I need help.

All options will be done to the back of the plywood attached to the acoustic panel

Option 1:
a layer of green glue then adding a second piece of plywood, whole panel screwed directly into door

Option 2:
1/8" mass loaded vinyl then adding a second piece of plywood, whole panel screwed directly into door

Option 3:
add 1cm of edead (rubber butyl) to the back of the single piece of plywood and space it off the door by an inch

**Ted White** · **10-28-09, 11:29 AM**

So you want to hang a massive panel on the door?

**Wayne A. Pflughaupt** · **10-29-09, 10:34 AM**

Moving to the HT Construction Forum...

I’m not sure this is going to get you anything. Typically a solid core, air-tight door is all you need. While your plan might better soundproof the door, there’s no gain in making it better soundproofed than the walls are, especially if they weren’t built for soundproofing (staggered studs, double or triple sheetrock, etc.).

Regards,
Wayne A. Pflughaupt

**goonstopher** · **10-29-09, 11:28 AM**

The walls are very thick and let almost no sound through into the other parts of the house. I will probably try green glue and a couple layers of thin wood/mdf

**Ted White** · **10-29-09, 11:30 AM**

So isolation is a goal? If so, you would want the ceiling decoupled to create a spring system. This is different from a suspended system.

**goonstopher** · **10-29-09, 11:38 AM**

The goal is to not let sound out into the room that the door leads to. That is all i am trying to achieve.

**Ted White** · **10-29-09, 11:41 AM**

OK so a beefed up door is the goal. Any chance sound could enter the ceiling and simply go over (flank) the walls?

**goonstopher** · **10-29-09, 11:46 AM**

I am obviously not even 10% as experienced in this as you so I am sorry if I am over simplifying it.

My goal is reasonably conservative. I want the sound to go from very loud and "bothersome" in the other rooms on the same floor to noticeable and manageable.

**Ted White** · **10-29-09, 11:52 AM**

No problem. I hope you don't mind the questions. You'd like to meet your goals without doing / spending what's unnecessary.

Having a super massive wall is a great starting point, obviously. If sound can enter the ceiling, it will travel up to the living areas above I assume there are). As well, sound entering the ceiling cavity can also travel laterally, and simply drop down in the room next to it. We describe this as Flanking Sound. Here's a short article to describe the concept: http://www.soundproofingcompany.com/...cles/flanking/

You have the wall taken care of. You can assess the ceiling and decide. After that. a solid core door that is sealed will help a lot.

**MatrixDweller** · **10-30-09, 11:21 PM**

You'll have to take extra care to soundproof the door jamb as well. Sound can flank around your massive door through the cracks in the shimmed door jamb. You'll want to seal the crack with green glue or elastomeric caulk. You'll also need a high end gasket and sweep system.

SOund is going to penetrate into the other room through the weakest point in your wall/door system. So if your door was super high 75 STC, your wall was 65, the ceiling that is shared between both rooms is 65, but the jamb around the door is only 50 then you will hear sound coming from the door jamb, albeit ~50dB quieter than in the noisy room. That also means that using a door that much over the STC rating of everything else is pointless.

If you do go for a heavy door then you'll also need to make sure the jamb is extra solid so that the extra heavy door won't pull it out of place. Standard finishing nails are not going to do the trick.

**Ted White** · **10-31-09, 12:50 PM**

I agree with Matrix. One small point:

Quote:

MatrixDweller wrote:

You'll want to seal the crack with green glue or elastomeric caulk.

Green Glue isn't a sealant. Only used between panels. Looks like a sealant, but isn't. You'd have quite a goopy mess if left exposed.

**glaufman** · **10-31-09, 06:09 PM**

Quote:

Ted White wrote:

I agree with Matrix. One small point:

Green Glue isn't a sealant. Only used between panels. Looks like a sealant, but isn't. You'd have quite a goopy mess if left exposed.

But the same MFR makes a sealant type product.

**goonstopher** · **10-31-09, 06:12 PM**

Where would you use sealant? Wouldn't it seal the door closed?

**Ted White** · **10-31-09, 06:17 PM**

Between the wall drywall and the wood jamb

**goonstopher** · **10-31-09, 06:41 PM**

What is a door jam? You mean the frame? the frame is 10 inches of thick food built into a plaster wall.

**glaufman** · **10-31-09, 07:37 PM**

Quote:

goonstopher wrote:

What is a door jam? You mean the frame? the frame is 10 inches of thick food built into a plaster wall.

Thick food? Like mashed potatoes?

Obviously I don't know the specifics of your construction, but typically...
When a room is framed out, openings are left for the doors, on either side you have a jack stud an da king stud "sistered" together. When the door it putin place it's frame is shimmed off the stud so it can be perfectly levelled. This creates an air gap that sound and heat and vermin can pass through. Cheaply, this is covered up with moulding, but better (in non sound critical applicaions) when it's filled with insulation, which can typically be a spray foam (expanding or not)... as I'm writing this, the spray foam may help soundproofing as well, but probably not as well as a material meant for the job.

Do you mean 10 inches from inside to outside? I think it'd be pretty unusual to have a frame 10 inches thick to either side of the door...

OK, so your wall is plaster... that required lathing behind the plaster, that lathing has to be mounted on something... studs

**goonstopher** · **10-31-09, 11:17 PM**

Yes the door frame is a good 10 inches thick, it is an OLD home. Some things are built like and others are WAAAY overkill.

**goonstopher** · **11-01-09, 11:41 AM**

DO you leave the screws in once the green glue dries?

**Ted White** · **11-02-09, 11:11 AM**

Yes, absolutely

**MatrixDweller** · **11-02-09, 02:45 PM**

Quote:

goonstopher wrote:

Yes the door frame is a good 10 inches thick, it is an OLD home. Some things are built like and others are WAAAY overkill.

Odds are that the molding is 10" wide which covers the jamb. It's most likely good and solid if it's in an old house and possibly made from hardwood. If you're lucky there is a solid timber running up from floor to ceiling that is thick. It's still a weak point where it joins the wall for sound flanking through and my point on the weakest link still applies.

If it's a plaster wall...is it filled with insulation of some kind, or is it hollow? Same with your ceiling and floor that are shared with the other room?

Also if the jamb has never had a door on it you'll have to make sure it's square and strong when you put the door on it. If you plan on making a heavy soundproof door then you'll probably need to use 3 or 4 heavy hinges with long screws that dig in to the wood framing.

A good door gasket is also required to maintain the the STC rating. Even a standard solid core door (like a Masonite Safe n Sound door) with a good gasket system in place will stop a lot of sound.

You'll want something to prevent the heavy door from being slammed shut also. If it's slammed it will put a lot of force on the wall system and could end up cracking your plaster.

**goonstopher** · **11-02-09, 03:08 PM**

Wow this is way more involved than I was prepared to get.

I hope a layer of MDF and one 3/16 of white primed board + 2 layers of green glue don't add too much weight...

Advertisement