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[ShakesTheClown]

Curious here, I know I'm opening a can of worms but, if I'm building a room inside a room, how much does is matter where I put the mass?

What are the merits of symmetrical construction as opposed to asymmetrical? For instance... Two layers of drywall, wood frame, insulation, air, wood frame, two layers of drywall - vs. - One layer of drywall, wood frame, insulation, air, wood frame, and three layers of drywall.

As long as it's all sealed up, how significant is the difference? I'm building inside an existing structure and I intend to remove the layer of drywall on the inside of the space and build inside it. Yes, I can add an extra layer to the outside of the existing wall but that would involve removing/replacing a few existing parallel walls, adding the second(or third) layer and then replacing the parallel walls.

Can I use the drywall that I remove from the inside leaf to reinforce the outside layer by green gluing it to the inside of the outside wall if I place it between the studs?

Now that I think about it, I'm willing to bet that the existing structure is built of 1/2in. sheets and I will be using 5/8in.

Thoughts?

[Thomas@Northward]

I would skip the Green Glue / Resilient channels etc, focus on a well thought-out wall assembly and add mass instead.

Here's a couple documents that will for sure help you too:

http://www.nrc-cnrc.gc.ca/obj/irc/doc/pubs/ir/ir761/ir761.pdf

http://www.nrc-cnrc.gc.ca/obj/irc/doc/pubs/nrcc41501.pdf

[ShakesTheClown]

Awesome! I'll be back in a week with more questions.

[franman]

I'm with Thomas on this one.. Build a simple, but massive wall... Watch your flanking paths and keep it simple.. 2x 5/8" - Stud(Insul) 2x 5/8"... Build it tight and seal it up. On Inner walls, we try to use a min of three layers (materials may vary) just to have a rigid leaf on the inside (of floating rooms). Rarely do we go over 4 layers (diminishing returns) because of mass law.

fm

[ShakesTheClown]

Ok, I've read and digested all of this but the math involved in the flanking study is waay over my head. I think I have a good idea of what needs to be done here but as always, there are lots of variables.

In the interest of full disclosure, there is an existing thread here...

http://messageboard.tapeop.com/viewtopic.php?p=632850#632850

[Thomas@Northward]

If you have neighbors, you'll have to float at least your Live Room. Otherwise, it's guaranteed problems.

How high is your ceiling (building structure) and what is the load bearing capacity of the floor?

If you can get us that data, then we'll be able to tell you what's feasible technically.

[ShakesTheClown]

Ceiling height is only 10ft to the underside of the roof supports. As it stands the drop ceiling is just short of 9 1/2 feet.

The floor is a solid concrete foundation so I'm pretty sure it'll support anything I throw at it.

Any ideas about what issues I'm going to have with the windows?

[Thomas@Northward]

Windows: not an issue.

Ceiling height: possibly an issue... If you have to float.

[ShakesTheClown]

Why would I have to float the floor if it's a solid slab? The building isn't on level ground but the slab is certainly level. On my end I'm sitting on about four feet of solid concrete.

[Thomas@Northward]

It's still to be determined if you need to float or not. Mechanical noise transmission is a tough monkey. If you take a risk and it turns out you have a problem, the whole project could be pretty much worthless and unusable. So it's best to investigate the current situation and needs and decide after. Keeping a major safety margin. Not floating = we are sure there are very limited risks. In case of a doubt: float. Floating isn't as expensive as people think wrt to the rest of the costs.

- Have you got plans of the whole building (including foundations & cross sections) in PDF or JPEG?
- Have you got direct neighbors?
- How much flanking are your ready to tolerate from LR to CR?
- How much vibrations from the nearby street are you ready to tolerate?

If you can post the pics & plans of your building here, I can for sure let you know what the first impressions are on that.

[ShakesTheClown]

Thomas, you are so kind to help me with this. Thank you.

I do not have plans of the building at all right now, I'm not sure I can even get them.

I do have direct neighbors. The studio office and offices for the record label/management company are next door. The wall is 1/2 drywall and insulation on wood framing. I can take out the inside (my side) layer of drywall if necessary but I can't build on their side. There is a hair salon on the other side of them.

I'm ok with a little transmission between the rooms. I built the place I'm in now(all the wrong ways) and It's just one smallish room with a 10x10x12 iso booth. I can always hear amps firing away in there so I guess I'm used to it. I really wish I had better isolation though. When checking drums I can always hear the fundamentals more in the room that through the speakers.

Vibrations from the street? How much should I tolerate? Will it be noticeable or is it just low frequency rumble?

[Thomas@Northward]

I do have direct neighbors. The studio office and offices for the record label/management company are next door. The wall is 1/2 drywall and insulation on wood framing. I can take out the inside (my side) layer of drywall if necessary but I can't build on their side. There is a hair salon on the other side of them.

Then I would float, no hesitation to have here. You cannot afford to have issues with your neighbors. They can have you closed down in a matter of days. Solidian transmission is the cause of a lot of  re-emission, and no matter how thick your walls will be, it's the building structure and THEIR wall that will vibrate and cause them to hear you. Even if they're far.

Vibrations from the street? How much should I tolerate? Will it be noticeable or is it just low frequency rumble?

You should not tolerate any. Even if barely audible. Once you start to compress, it will be difficult to manage. But that can be assessed by doing some measurement over a few days.

To reassure you: both these issues are taken care of or improving when floating.

[boggy]

I agree with Thomas.  Nick has at least two reasons to build a (serious) floating floor. Neighbors and street traffic.
Solid (concrete) slab on ground is a cheapest/easiest way to build a floating floor because there aren't load-bearing capacity problems.

[rjc]

Then I would float, no hesitation to have here. You cannot afford to have issues with your neighbors...

Yes, absolutely. It's not just about ensuring your neighbours won't complain and/or have you shut down. You also need to deal with impact noises, footfalls and dropped items etc finding their way from your neighbours' spaces into yours and onto your recordings. This is potentially at least as serious an issue as rumble and vibration from the street (the noises may be less frequent, but no less problematic...).

[ShakesTheClown]

You should not tolerate any. Even if barely audible. Once you start to compress, it will be difficult to manage. But that can be assessed by doing some measurement over a few days.

What kind of measurements are we talking about here?

Also, what mind of construction would you recommend here for the floors and ceilings?

[Thomas@Northward]

What kind of measurements are we talking about here?

Also, what mind of construction would you recommend here for the floors and ceilings?

If needed we leave a measurement rig for a few days to measure various levels in continuous (noise, vibrations). Not very expensive usually.

A floating floor isn't hard to implement, but the calculations need to be very well done and the design well though out. There are only a few ways you can do that anyway. There is a thread from a few weeks ago that references different providers of such systems.

http://repforums.prosoundweb.com/index.php/topic,984.0.html

But you will need an engineer (structural or acoustician) to calculate that for you and do the floor / "box-in box" design.

[ShakesTheClown]

This is pretty intimidating.

Any suggestions of who I would contact near Dallas, Texas?

[franman]

Nick,

I can only agree with the advice to float a proper floor and room for your location. Where are you?? Concrete floating floors are fairly 'permanent'.. Is this a lease of own situation? What type of ceiling height do you have to start with?? These are all serious questions that need to be considered...

The measurements are straight ahead hi res LF airborne tests as well as some type of accelerometer measurements to quantify the level of structure borne vibration. From the info provided you will need some type of relatively heavy floating room to mitigate the street noise (vibration) and to do this without bothering your neighbors.

FM

[ExcuseMe]

Maybe I'm too new to understand some of this, but I didn't think sound-proofing some walls or even a room was that huge of a deal.  I've seen people use all sorts of things, with various results.  Of course using superior equipment is better, but I've seen people use sound curtains and egg cartons and get pretty good closure. 

[franman]

I'm sorry ExcuseMe, but curtains and "egg crates" have no effect on sound proofing (sound isolation). These are both low tech solutions for sound treatment and arguably have little effect in that use either (well, the curtains will certainly absorb high/mid frequencies, but the egg crates?? I don't know....)

With regard to sound isolation or "sound proofing" mass and air space are required and a scientific approach is the best way as it quantifies what the existing STC (sound transmission class) is based on the existing construction, and how much improvement is required. Of course, all things are budget driven so sometimes, we just specify the best solution a particular customer can afford...

The distinction between sound isolation (construction) and acoustic treatments is an important one that our clients (and readers) should understand so we can better discuss questions relating to these two broad and separate topics... No flame intended at all.. just clarification.

FM

[franman]

Nick,  Ironically I will be in Dallas this coming week, but I'm totally booked up for the two days I'm there. Russ Berger is local, but I doubt he will get involved unless there is a real budget. I'm in and out of Dallas for the next few months on construction review of another project. If you would like to discuss a consult, let me know...

Also you can contact Mark Genfan at Acoustic Spaces (based in Austin). He's an old friend and I'm sure he could help you out. (he's on the forum but I can't recall his username....)

FM

This is pretty intimidating.

Any suggestions of who I would contact near Dallas, Texas?

[Genfan]

Thanks Fran--already been talking to Nick for a week or two! Looking at solutions that meet reality of budget situation. 

[franman]

Nick.. his username is Genfan...

[ShakesTheClown]

Ha!

[ExcuseMe]

Oh, I'm sorry.  I didn't catch that we were specifically talking about sound isolation.  Yeah, low-tech soundproofing isn't going to do much for that.  I have had some luck with sound curtains and sound isolation, though.  The better quality ones do market to that.  I agree that sound isolation is important and should be done well, though. 

[Wireline]

Nick, a couple of thoughts from a fellow Texan in a strip mall locale...(I'm in Midland)

- Windows:  when the wind starts blowing like a banshee, those huge windows can resonate loud enough to hear.  What we ended up doing was putting up interior bracing to stabilize them, R19 in the spaces, and decorative boarding on the outside - also gave the place a much higher security level.

- Ceiling: You not only share a slab, but a roof - that's been our biggest battle.  When planning to make the room in a room thing, plan for that, as well as extending HVAC, etc...

- Future Building:  I don't know where you are in Dallas, but where I leased in Midland has dramatically changed over the past 3 years...Since I've been at the current location, major construction has gone on with 1/4 mile of me, thus making isolation (and dust) control almost impossible.  Check with the city to find out if there are building permits - if so, plan to add more isolation now, as its a lot cheaper now than to retrofit.

- Neighbors: before laying down one piece of wood, find out who your neighbors are and get friendly with them.  Two weeks after I opened, the place next door decided to become a loud bar with bands and a full liquor license - changed their noise level so in my tracking area with their bands playing, I was reading 60dB!!!  Took the city council to intervene.

Just some more things to think about regarding noise...

[franman]

Ken,

That is ALL very good advice! the part about future building and knowing thy neighbors should be advice for all those considering construction in commercial locations.

FM