double layer RC, single stud vs. double layer staggered stud

jordya · Post by **jordya** » Sat Aug 06, 2005 4:26 am

Hello,

I have read many of the posts regarding STC and wall mass. The SAE chart was great. My question is how do you figure STC rating when you mix and match from their examples?

My case in point: I would like to build a wall that has a STC rating of at least 50, preferably 55+. On the SAE chart, a staggered stud wall with 2 layers on each side will get you an STC of 54, with insulation.

A single stud wall with one layer on each side and a RC will get you an STC of 47 with insulation.

My question is, if I add a layer to each side of the single stud wall, will that create the same STC rating as a staggered stud wall with 2 layers?

Also, is there a formula for figuring these unique situations out for yourself? I searched but could not find anything for my situation.

Thank you,

Jordy A.

AVare · Post by **AVare** » Sat Aug 06, 2005 5:02 am

I'm runing short on time so this is short. Canada's NRC published a report for the actual testing of 350 wall designs called IR-761. It is a daunting I think Stee has link in the stickies to it.

STC is really not suitable for music isolation. Looka the TL curves.

Anjoy!
Andre

drfrankencopter · Post by **drfrankencopter** » Sat Aug 06, 2005 5:16 am

IIRC, a double drywall single stud plus RC wall has about the same STC as a staggared stud double drywall construction. There's some differences in the low frequencies (where I think RC has some deficiencies). Like Avare said, really with music, TL is the main issue. Look at the performance of your wall at around 80hz or so. This is what people will hear and complain about (kick drum and bass guitar).

Cheers,

Kris

jordya · Post by **jordya** » Sat Aug 06, 2005 5:50 am

ok, so am I correct in saying that double wall is better for low frequency TL than a staggered stud wall?

If that is true, is there a big difference between the two choices?

I am trying to save on as much space as possible, but after reading this and other posts, I am seeing why my current studio bleads out the drums, but you can't really hear the guitars or anything. Its because the wall is not staggered or a double wall.

Thanks again for all the help...

AVare · Post by **AVare** » Sat Aug 06, 2005 6:54 am

If that is true, is there a big difference between the two choices?

That is an amazingly general question. Read, okay it is over 300 pages long, study, IR761. It has single, staggered, double, wood, steel, rc walls in it. Here is the link to it.

URL NRC IR761

There are many ways to answer your question while stil being correct. Kris gave a good summary at one level. It is your studio, your money, your home. The more you study and learn, the beter you will be able to make your life better. Keep the quesiotns coming as you have them. We love helping people. We love even more helping people who are helping themselves.

Andre

jordya · Post by **jordya** » Sat Aug 06, 2005 8:58 am

wow, that helped a lot. Thanks. From that info, I'm still not sure which way to go. Granted, I have time to decide but I'm just getting anxious to build my new studio.

Am I right in saying that 20Hz to 250Hz is the range for kick drum and bass guitar? If that is true, then the double walls have a better TL rating...almost 10dB difference when you compare it to a staggered stud wall with the same features...2 layers gypsum on each side and the same insullation.

I guess there is no perfect way to do it...just figure how much space and money I have and go from there. BTW, if a double wall is 2 seperate walls that are not touching each other, what are they attached to to remain sturdy? Or is it you build the parameter of the room, then build it again, just inside of the first, making a double wall.

Post by **sharward** » Sat Aug 06, 2005 9:53 am

You are correct that double frame kicks butt over single stud frame with staggered studs. Not only do you have less flanking, but you have a wider air gap, which is critical to achieving decent TL in the low range.

AVare · Post by **AVare** » Sat Aug 06, 2005 11:47 pm

jordya wrote: Am I right in saying that 20Hz to 250Hz is the range for kick drum and bass guitar?

...I guess there is no perfect way to do it...just figure how much space and money I have and go from there. .

Kick usually peaks in the 50 to 80 Hz range. Bass guitar has fundamentals (not that strong fortunately for islolation) either 41 Hz for normal 4 string or 29 Hz for 5 string.

The last line I quoted is almost competely correct. Money and space get int he way of perfection.

The more you know the compromises ,the better it can be made to your satisfaction.

Andre

drfrankencopter · Post by **drfrankencopter** » Sun Aug 07, 2005 12:25 am

Money and space get int he way of perfection. Smile The more you know the compromises ,the better it can be made to your satisfaction.

This is the truth right above! If you go into your construction with realistic goals, you are far less likely to be dissatisfied by the results. Having a successful project and being on budget depends intimately on what consider "good enough" for your needs.

Always consider what the weakest link is in your sounproofing chain. There's not much point in having STC 63 walls if your ceiling is STC 35 and your trying to keep from waking the people upstairs.

Cheers,

Kris

the dreamer · Post by **the dreamer** » Sun Aug 07, 2005 1:22 am

jordya wrote:BTW, if a double wall is 2 seperate walls that are not touching each other, what are they attached to to remain sturdy? Or is it you build the parameter of the room, then build it again, just inside of the first, making a double wall.

You have mor options here:
Buuild both walls conecterd to the same floor/ceiling. Good isolation. Maybe flanking is becoming the weakest link.

Or you go by building a room-in-room construction. Excellent isolation but expensive. This means that (we skip the floating floor here) the inner wall will bear the inner ceiling.