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Old 7th June 2020
Gear Head

Realistic/Real World STC of Sound Isolation Clips?

Hey folks,

My kick drum in my unfinished basement reads at 74.7 db when on the first floor and 54.9db on the second floor. If I soundproofed my basement with insulation, isolation clips and 2 layers of drywall and greenglue for both the walls and ceilings and solid core doors with air gap treatment, will it realistically bring those levels down low enough that it won't disturb people in the rest of the house at both 1PM and 1AM?

I'm building a jam and recording studio in my currently semi-unfinished basement, which includes drums, mic'ed vocals, and amped guitars and mostly plays heavy/thrash metal. The space consists of one 1' x 2' window, 1 exterior door, and 2 interior doors which both lead to another side of an already finished basement. I have a family of 5, and I'm the only guy, so you understand the concerns.

Currently, if I play the kick drum heavy and I use a sound meter (just an app on the phone) in the 1st floor living room right above it, I reach a max 74.7 db. If I go to the second floor bedrooms, which luckily is not directly above the basement, I reach a maximum of 54.9 db. So, I feel like I'm starting at a reasonable point, agree?

The perimeter 2x4 walls are already up (house came that way), so I plan to use insulation (insulation is already present in the walls but not the ceiling) with isolation clips and 2 layers of 5/8" drywall and green glue in between. Similar for the ceiling. Also plan to replace the doors with solid ones and getting those door soundproof kits to remove the air gaps around them.

My question is with my first floor at 74.7 db and second floor 54.9 db, is it realistic to think I can get it to a level that I can play while someone is watching the tv in the living room and not be annoyed, or while the kids are going to bed or at 1 AM with the family asleep and no one will wake up?

Greenglue states their isolation clips have an stc rating of 61 with 2 layers of drywall, which if true I think would bring it to a quiet enough level? But are those real world numbers? Do most people actually achieve that? Or should I expect more like an stc of 30? Also, since a second layer of drywall only adds an extra 5 STC, given my current specs is it worth it to add or should I just go single layer, which has an advertised stc rating of 56?

Thanks in advance