What would be my STC number for wall?

[Pancreas]

I live in an apartment that I own. Since I play guitar and listen to low music, but I’d rather not here anyone, I did some “sound proofing”

The walls here is pathetic 3/8 with zero insulation. The good thing is the studs are metal. The outside wall around window is concrete. The floor and ceiling is concrete.

Only one wall is adjacent to neighbor. This is the wall I did some work on. Since 3/8 with metal studs without insulation.

Instead of tearing down the wall, I had someone install wooden studs on top of the 3/8 wall, put fiberglass insulation around it, then a 5/8 wall on top of it.

This was the cheapest option as anything else like resilient channels and other forma would have been way more expensive

Also tearing down the original wall to add insulation, then replace wall, then another wall on top of that one would’ve been more expensive

I wonder what STC I may have now with this setup.

I also replaced the hollow door with solid core one.

 

[JSmith]

I wonder what STC I may have now with this setup.

I assume you do not know the STC of the new and old part of the wall?

Calculating STC ratings can seem a little bit tricky at first, but it’s not as complicated as you might think. Determining ratings for windows, walls, and ceilings all happen the same way defined by the ASTM E90 standard. The first step in rating a product is to determine the transmission loss of the material at various frequencies. Two rooms with measurement equipment are divided by the material, one designated as the source room, the other as the receiving room. The sound pressure levels in both rooms are compared at various one-third-octave band frequencies from 125 Hz to 4000 Hz. The difference is used to calculate the transmission loss of the material at each of the frequency bands. Each transmission loss value is plotted on a graph then compared to a standard set of STC contours, with the closet matching contour determining the STC rating of the material. If your results most closely resemble the curve for an STC rating of 50, then that would be the rating for the material you tested.

STC Rating: Understanding Sound Transmission Class Rating | ASI

The STC rating is important when you are trying to reduce the amount of sound entering or leaving a room. Read more about it!

www.acousticalsurfaces.com

JSmith

 

[Pancreas]

Well I can’t get into the neighbors apartment to do measurements lol

But i went from basically

3/8 metal studs to neighbors 3/8 with metal studs which is how I assume it was

5/8 -> insulation -> 3/8

Im assuming I may be at 45 at least with is the minimum

 

[LouB]

I've built studios, home theaters & multi family buildings where STC ratings were crazy some tested after install, some built to US gyp specs, some bulit per THX designers. I can't remember ever seeing a 3/8" gyp wall ever tested or considered. I doubt your at 45 but without testing you'll never know.
What you need in your situation is mass, I'd use 3 layers of 5/8" gyp. on your 1 sided wall stagger and caulk or tape all joints & screws between layers and caulk wall and ceiling butt joints with acoustiacl caulk every layer. Yous pads on any elec box penetrations and insulate your wall R30. Also make sure you have at least a 1/2" gap from your sound wall to the party wall. With this you may get to 50-55
There are a lot of assemblies on line. But if your ceiling isn't treated and not isolated from your neighbors the wall STC rating is useless. When it comes to STC ratings think of like a boat where a small leak will still sink the boat. Also sound can transfer through floor assemblies also, isolation is the key.

Here ya go, https://www.nationalgypsum.com/who-...cal-wall-designs-variables-affect-stc-ratings

 

[BlackTalon]

@Pancreas , did you cut into the wall before adding the new materials? it would not be normal in the US to have a wall between adjacent units that consists solely of one plane of studs with a 3/8 gyp board layer on each side and no insulation. If there is only a single layer of gyp board on each side they likely would have needed to install staggered or double studs to meet STC requirements.

Some single stud systems exceed STC-50 by using multiple layers of gyp board on at least one side of the wall.

For reference, here is a guide to current ratings from USG: https://www.usg.com/content/dam/USG...ound-performance-selector-guide-en-wb2880.pdf

 

[Pancreas]

@Pancreas , did you cut into the wall before adding the new materials? it would not be normal in the US to have a wall between adjacent units that consists solely of one plane of studs with a 3/8 gyp board layer on each side and no insulation. If there is only a single layer of gyp board on each side they likely would have needed to install staggered or double studs to meet STC requirements.

Some single stud systems exceed STC-50 by using multiple layers of gyp board on at least one side of the wall.

For reference, here is a guide to current ratings from USG: https://www.usg.com/content/dam/USG...ound-performance-selector-guide-en-wb2880.pdf

I think there is double studs

I did cut into the original wall, the handyman. I did for the bathroom area that had some mold though. I also had my bathroom renovated. I didn't measure the original drywall but it looks like 3/8 to me as these apartments were built in the mid-70s.

Actually, now that I remember, there is insulation in the original wall but is cork.

So basically is the metal studs, the cork insulation, and the 3/8 drywall. That's for all the walls.

Then, I had a handyman add wooden studs on top of the 3/8 drywall, put bat insulation around it, and 5/8 drywall on top, then I sealed all possible cracks with the acoustic sealant.

I don't know how much improvement I gained, but it was the cheapest option tbh and is done, so i dont know if i could anything else, sometimes i wish i would have use concrete or something lol tho i dont know if it would be feasible