Soundproofing a room - results less than hoped

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Soundproofing a room - results less than hoped

Postby Bob » Mon Oct 06, 2014 3:42 am

AVS-User "granroth" has been doing a fair bit of his own work trying to figure out how to do soundproofing right,
and got less than he expected in today's measurement.
If you have a moment, feel free to wander through his thread and see if you can spot why.
Lots of pictures and descriptions of his construction.
http://www.avsforum.com/forum/19-dedica ... hread.html
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Re: Soundproofing a room - results less than hoped

Postby Yannick » Mon Oct 06, 2014 10:07 am

I just looked at the final posts.

two ideas:

a. the is probably a LOT of flanking noise through the windows. In my unfinished mastering studio, when the inner glass pane was not put in yet (in front of an outside window) I could still clearly hear the piano room. I have no measurements, but my guesstimate would be a 30dB improvement when the glass was fitted.

b. he is probably comparing an incredibly reverberant room to a previous state, where there was less isolation, but much more absorbtion in room ?

I would cover up the windows with some wood panels and remeasure.
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Re: Soundproofing a room - results less than hoped

Postby bert stoltenborg » Mon Oct 06, 2014 10:10 am

Can he make a summary?
This is way to much.

Why isn't he using pink noise or a sweep for measuring? This is asking for S/N-problems in the LF-region, IMHO.
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Re: Soundproofing a room - results less than hoped

Postby drnelson » Tue Oct 07, 2014 6:48 am

Bob,
He is not that far from me, 30 minute drive. I could go look at it if he is willing. Looking quickly through the posts it looks like he did most things right but it is easy to overlook things that will short circuit the isolation. Have him join here and send me a PM.

Dan
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Re: Soundproofing a room - results less than hoped

Postby Bob » Wed Oct 08, 2014 12:00 am

drnelson: He might just do that, if he hasn't already.
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Re: Soundproofing a room - results less than hoped

Postby Bob » Wed Oct 08, 2014 12:02 am

Bert:

re "summary"...

Click for larger
Image
Letters indicate sound volume testing points.

granroth wrote:- Three exterior walls [ 7.5" {hollow concrete} block, 1" polyiso solid form insulation, 1" air gap, 2x4 studs @ 24" O.C w/ R-13 fiber insulation, 5/8" Type X Drywall, Green Glue, 5/8" Type X Drywall]
- Ceiling [5/8" Type X, Green Glue, 5/8" Type X (or 5/8" OSB in two places), room-in-room floating 2x10 joists, missing insulation, attic]
- Floor [concrete slab]
- Non-block East wall section [5/8" Type X, Green Glue, 5/8" Type X, 2x4 studs @ 24" O.C w/ R-13 fiber, 1'-2" air gap, 2x4 studs @ 16" O.C w/ R-13 fiber, 3/4" particle board between studs, 1/2" drywall]
- East section North wall [5/8" Type X, Green Glue, 5/8" Type X, 2x4 studs @ 24" O.C w/ R-13 fiber, 1" air gap, 2x4" studs @ 16" O.C w/ ~R-13 fiber, 1/2" drywall, bathroom cabinets, mirrors, etc]
- Center section North wall [5/8" Type X, Green Glue, 5/8" Type X, 2x4 studs @ 24" O.C w/ R-13 fiber, 1" air gap, 2x4" studs @ 24" O.C w/ R-13 fiber, 3/4" particle board, Green Glue, 5/8" Type X, missing planks]
- West section North wall [5/8" Type X, Green Glue, 5/8" Type X, 2x4 studs @ 24" O.C w/ R-13 fiber, 1" air gap, 2x4" studs @ 16" O.C w/ R-13 fiber, 1/2" drywall]

- Door [3/4" MDF, Green Glue, 1-3/4" solid core door, Green Glue, 1/2" MDF]. Also has "automatic door bottom" of unmentioned type, but not Zero International.

- HVAC [missing]

As mentioned above, I'm currently missing the attic insulation, but it will eventually be R-50 blown cellulose EXCEPT for the parts that will touch both the exterior and interior walls -- those will have loose fiberglass batts. The center section of the North wall will eventually have a layer of 1/2" reclaimed hardwood planks, entirely as a decorative element.

I haven't yet decided on the HVAC and so the theater currently has none at all.

I can put my SketchUp file somewhere, if anybody wants it.


Image

Image
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Re: Soundproofing a room - results less than hoped

Postby bert stoltenborg » Wed Oct 08, 2014 6:37 pm

Let's wait for Dan's opinion before starting the guessing game. :D
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Re: Soundproofing a room - results less than hoped

Postby drnelson » Thu Oct 09, 2014 5:13 am

I have not heard from them yet. I would say what he is getting is about right for the door. I think the door is likely to in the STC30 range if it seals completely. I didn't see anything about how he was doing the HVAC ducts either but I might have missed it.

Dan
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Re: Soundproofing a room - results less than hoped

Postby Bob » Thu Oct 09, 2014 7:14 am

drnelson wrote: I would say what he is getting is about right for the door. I think the door is likely to in the STC30 range if it seals completely.
My guess would have been STC 38 as the top end with magnificent seals.

drnelson wrote: I didn't see anything about how he was doing the HVAC ducts either but I might have missed it.

He has no HVAC. None. No forced air. No return air.
I think he had something in mind for Heating/Cooling, but I think he's not planning on ventilation -- I don't recall.
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Re: Soundproofing a room - results less than hoped

Postby Bob » Mon Oct 20, 2014 6:57 am

Granroth wrote (at AVS)
On my soundproofing disappointment front, Bob hooked me up with Dr Nelson who founded studiotips.org, and who happens to live locally. He stopped by and we inspected my theater and discussed quite a few related topics. In the end, he said that my suspicion that the door was my weak link was correct, as it couldn't be better than STC 38, while my walls are easily STC 50 or higher. He also pointed out a few air leaks in my first layer and gave some hints on correcting that. We also discussed some ways of maybe using the upcoming barn door more effectively, although his suggestion was to just create the barn door as is and test it without any special treatments. If it did enough with no treatments, then just stop right there.

I did make one arbitrary decision while talking it over with him -- and that's to go back over the door jamb and cut a gap between the two parts. He concurred with Rod Gervais that having the jamb connected likely won't make a huge difference... but it'll definitely make some difference. I finally realized that I'll likely always have this tiny sliver of doubt about that jamb if I don't decouple it and now's the time, since all I need to do to access it is unscrew my door stops. Nothing is glued, yet.
Regards
Bob Golds
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