# When is the STS score considered good?



## MLGamer (Feb 10, 2013)

Hello one and all,

I have finished planning my acoustical and soundproofing designs for my soon to be constructed home theater. My full soundproofing and acoustical plan includes:
1. Green glue between 2 5/8" drywall sheets. This will be done on the entire lower level.
2. Back boxes for all speakers (Triad system is all in-wall, in-ceiling)
3. Bat 15 (walls) and BAT 30 (ceilings) throughout. 
4. Sound panels -Based on my floor plan, 10 of various sizes should do the trick (see attached floor plan)
5. Green Glue sealant on throughout as needed
6. All doors will be solid core throughout the project area
7. Bass traps in the screen left and right corners
8. Added a solid core door at the bottom of the stairs
9. Staggered stud wall construction
11. Isolation clips and channeling for the entire ceiling
12. Door treatments
13. Window treatments

My questions is this: what is considered a good or even excellent STC score? I am finding you can spend as much as you want on sound and acoustics and still have more options to consider. My goal is to make the lower level, which will be fully finished (see plan), soundproof to the point of not disturbing my wife sleeping. The home theater is located directly below the master bedroom. I am even considering using a dampening treated drywall, such as Suppress, for this entire area.

Thanks for your responses and have a blessed Christmas.

~Matthew

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## bpape (Sep 14, 2006)

Good luck if the master is directly above the theater. You can certainly do a lot to reduce transmission and you're doing a lot of it. STC 55-60 would be pretty good but understand that STC does not really take into account the very low subwoofer frequencies and is an average of frequencies from 125-4kHz. It's really more for voice only. 

If you figure the bedroom upstairs has a noise floor of say 35 (very very quiet) and you have a wall that will do well at say STC60 and do pretty good at low frequencies (2x 5/8 drywall on both sides and green glue on both sides) then you should be able to play at say 80-85db and not really bother her much unless there is a ton of very low frequency information. 

85db minus the 60 STC for the structure leaves 25 which is lower than the noise floor in the room above.

You can improve your isolation by doing another layer of ply or MDF to the underside of the floor of the bedroom between the joist cavities with Green Glue. Right now you have 1 layer on the floor and 2 layers on the ceiling below, which is approx STC 52 - giving the benefit of the doubt that the subfloor will provide as much isolation as 5/8" drywall.


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## NBPk402 (Feb 21, 2012)

Subscribed... I am in the same situation as you with the MB over my proposed HT.

Would a layer of OSB and then 3 layers of sheetrock with green glue make the ceiling better or would that end up being too much weight?


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## MLGamer (Feb 10, 2013)

bpape said:


> Good luck if the master is directly above the theater. You can certainly do a lot to reduce transmission and you're doing a lot of it. STC 55-60 would be pretty good but understand that STC does not really take into account the very low subwoofer frequencies and is an average of frequencies from 125-4kHz. It's really more for voice only.
> 
> If you figure the bedroom upstairs has a noise floor of say 35 (very very quiet) and you have a wall that will do well at say STC60 and do pretty good at low frequencies (2x 5/8 drywall on both sides and green glue on both sides) then you should be able to play at say 80-85db and not really bother her much unless there is a ton of very low frequency information.
> 
> ...


bpape,

Thanks for taking the time to fill in some gaps for my project. I really appreciate it.

What about Suppress? Take a look at the STC ranges on this page: http://www.supressproducts.com/drywall.php

I am specifically interested in the SED3448 and SED4448. I spoke with a rep a few days ago that thinks the 3448 will get me in the 60 range independent of any other treatments. That appears to be pretty good. In addition, I could upgrade my framing to double stud which, according to the research I have done, can make a big difference. I know Suppress is expensive; however, money is not the primary consideration; instead, creating the best acoustically and soundproofed room with the best speakers I can afford is key. In short, I want to make the best home theater possible on my budget.

With much appreciation,

Matthew


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## phazewolf (Feb 5, 2012)

Not sure how much this will help or not but take your subs into the room even if it is not built and play some very bass heavy music at around 90db. Then go into the master and measure and see how much of a issue you have with the blank room this is only useful as a reference but you can then have a before and after if you play the same music and match the level.

Plus it will give you a good heads up on where things stand before you start. It may turn out there is not as much of a issue as one may think or you may see that you are going to have a long road ahead of you.

And if you do this please post before and after numbers this could help a lot of people down the road.

Also have you though of using limp mass vinyl damping between the sheets of drywall?


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## bpape (Sep 14, 2006)

A lot depends on the material vs labor cost. If you're going to DIY - Doing 2 layers of standard 5/8" with Green Glue will do as good or better job than a layer of the thick suppress. The staggered stud helps a LOT. The other thing to consider is having to have additional help. The 4448 1" Suppress is over 120 lbs per sheet.


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