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Soundproofing a room in basement

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spiral scratch

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I was thinking about soundproofing a room in my basement. The room is approximately 11 ft x 20 feet with 8 foot ceilings. I was planning to put some sort of soundproofing channel on the ceiling and along the interior wall plus add some insulation inside the the joists while I’m renovating and leave the two exterior walls as is.

I figure there’s likely to be noise escaping along the exterior walls and HVAC. There’s HVAC running inside the ceiling and there’s a bulkhead in the corner that’s about 6 feet long and a couple of feet wide.

I don’t want to build the room inside the room as is generally advised. There’s also a closet at one end of the room with a double set of sliding glass doors and I don’t want to bother too much with that either. I guess I’m wondering if the soundproofing efforts on the ceiling and one wall are worth doing if I leave the closet as is. Maybe I could add some baffles inside the HVAC to help isolate them. I really just want to help keep the noise from entering the rest of the house. Realizing that it’s generally recommended as an all or nothing type endeavour I’m thinking that it’s likely not worth the bother but maybe there’s an approach I’ve missed.

If anyone has any experience, suggestions or advice in this regard that would be appreciated. Thanks.
 
I live near an airport. What is common practice in my area is insulation, sound isolation clips, staggered studs in walls, and the use of multiple layers of drywall or QuietRock Drywall

You need to have a contractor that understands noise isolation construction practices as the best material will be of no use if proper construction practices are not used.

If you have not yet done so, you might consider spending the time to rank the noise leakage paths from the worse to least. I would put a loud sound source in the room and use a sound meter (or a phone app) to see what the paths are and what adjacent living areas are really impacted.

You can add an additional ceiling layer with isolation clips, but as you state the ducts can be a real challenge. I assume from your comments that there is little or no noise from HVAC ducts (from moving air, rattles etc) but you are worried about room to room transmission noise. Do they transmit sound now between? Are they metal ducts or flexible? They do make sound insulation ducts and baffels that I have seen used to address just a specific hvac run.

You might want to research at a forum that is dedicated to this problem: Dedicated Theater Design & Construction
 
Maybe you should elaborate a bit on construction details, om how much sound reduction you need at what frequency bands, etc.
Physics don't care about your preferences and if you fuck up on the weakest chain ypu know what will happen.
 
Thank you for your responses.

keithm55 said:
If you have not yet done so, you might consider spending the time to rank the noise leakage paths from the worse to least. I would put a loud sound source in the room and use a sound meter (or a phone app) to see what the paths are and what adjacent living areas are really impacted.
Click to expand...

This seems like perhaps a good place to start.

keithm55 said:
I live near an airport. What is common practice in my area is insulation, sound isolation clips, staggered studs in walls, and the use of multiple layers of drywall

You can add an additional ceiling layer with isolation clips, but as you state the ducts can be a real challenge. I assume from your comments that there is little or no noise from HVAC ducts (from moving air, rattles etc) but you are worried about room to room transmission noise. Do they transmit sound now between? Are they metal ducts or flexible? They do make sound insulation ducts and baffels that I have seen used to address just a specific hvac run.
Click to expand...
This is sort of what I had in mind without the staggered stud wall.

My main concern with the ducting is as a noise conduit into the rest of the building and my overall main concern is room to room noise transmission. My environment is pretty quiet so I'm hoping to minimize my impact on it.
bert stoltenborg said:
Maybe you should elaborate a bit on construction details, om how much sound reduction you need at what frequency bands, etc.
Physics don't care about your preferences and if you fuck up on the weakest chain ypu know what will happen.
Click to expand...
 
I removed the ducts and installed a minisplit for my basement media room to avoid the acoustic path into the rest of the house. The walls and ceiling are double-thickness drywall "floating" on Kinetics Noise Control IsoMax clips with 6" Rockwool behind them. The builder and drywall team liked that construction was pretty much "normal" drywall. Door is a heavy exterior (solid core) door with full weather seals to reduce sound transmission through the door. Construction aide I provided to the crew is below; additional details were provided by Kinetics Noise Control documents and me as needed.

HTH - Don

2008 Media Room Diagrams reduced.jpg
 
DonH56 said:
I removed the ducts and installed a minisplit for my basement media room to avoid the acoustic path into the rest of the house. The walls and ceiling are double-thickness drywall "floating" on Kinetics Noise Control IsoMax clips with 6" Rockwool behind them. The builder and drywall team liked that construction was pretty much "normal" drywall. Door is a heavy exterior (solid core) door with full weather seals to reduce sound transmission through the door. Construction aide I provided to the crew is below; additional details were provided by Kinetics Noise Control documents and me as needed.

HTH - Don

View attachment 438408
Click to expand...
Lots of nice detail. Thanks. I believe I saw your drawings in another thread here while i was researching. I like the duct encasement idea. I don't know what a "mini split" is. I'm not sure about losing another 3 inches of my ceiling height with the double 2x4 arrangement as it's not a very high ceiling to begin with but I can see the benefit in the added layering. I would probably consider boxing in the duct with drywall and arranging the drywall hangers below that.
bert stoltenborg said:
Maybe you should elaborate a bit on construction details, om how much sound reduction you need at what frequency bands, etc.
Physics don't care about your preferences and if you fuck up on the weakest chain ypu know what will happen.
Click to expand...
I quoted you and didn't add my reply. I don't have a lot of detailed plans, I was thinking along the lines of what Don has done, but maybe not to the same extent. The room is 11 x 22 feet with a 8 foot ceiling. There's two exterior walls and two interior walls. I was thinking to address the interior walls and ceiling with soundproofing and leaving the floor and exterior walls as they are. I don't need a super isolated room, I'm just planning to set up my stereo gear in there and listen to music. I don't tend to play my music really loud but occasionally I play it loud enough to compete with people talking. I was just considering how much effort I might give to decreasing sound transmission into the rest of the house.

I understand that the effort will only be as good as the weakest link. I'm trying to decide if my weakest links can be sorted. I think the biggest problem in the room to overcome is the 11 foot closet at the end of the room. It's made up of four large mirrored doors on sliding tracks. I would have to come up with a different closet design. I'm not sure I'm ready to tackle that yet. There's also a duct bulkhead inside the room located just above the doorway. I'm not sure I can provide enough clearance for properly soundproofing it without turning it into a huge obstruction. Rerouting duct work isn't really an option. I'm not planning on staying forever, but I needed to address some structural and mechanical problems which necessitated removal of the ceiling. I was thinking now that that's done maybe I can make this work better. Hope that helps.
 
spiral scratch said:
Lots of nice detail. Thanks. I believe I saw your drawings in another thread here while i was researching. I like the duct encasement idea. I don't know what a "mini split" is. I'm not sure about losing another 3 inches of my ceiling height with the double 2x4 arrangement as it's not a very high ceiling to begin with but I can see the benefit in the added layering. I would probably consider boxing in the duct with drywall and arranging the drywall hangers below that.
Click to expand...
You can just mount the clips and isolation strips along whatever studs and joists you already have. I honestly am not sure why I added the extra boards at this point; it may have been for additional isolation, or something about the building code since I had to add an outside air path (not to the house, secondary ventilation). It dropped my 9' ceiling to about 8' 6" so not a horrible hit but annoying.

A mini split is a ventless HVAC system with a quiet fan/heat exchange unit inside and all the loud stuff is outside. Fujitsu and Mitsubishi are two popular manufacturers but there are others. Example: https://www.fujitsugeneral.com/us/products/split/index.html
 
Last edited:
While general talk is always helpful, it is up to details. Different task to stop 20hz at 115dB than 105dB at 1khz. The first not really being possible at all, but could be mitigated to some extent (mostly by rolling it off though).
 
The two folks above that linked you to the theater building forum on AVS have sent you to the right place. Go there an ask your questions. I just finished (as in last week) building a soundproof room in my basement, and most of what I learned about the process I learned there. That forum is extremely helpful and very knowledgeable for building rooms like this.

Soundproofing is mass, damping, and decoupling. Sound is transmitted by waves vibrating the drywall, which vibrates the studs, when then vibrate everything attached to them (other studs, the drywall on the other side, the house framing, floors, etc). Those material vibrations are what you hear on the outside of any room when the door is closed.
  • More mass (more drywall) takes more energy to vibrate.
  • Damping (green glue) further reduces the vibration by converting it into heat between the layers of drywall.
  • Decoupling uses rubber bushings to float a whole studded wall (DC-04 clips) or to hang hat channel (RSIC-1 clips). It is also used to isolate other large objects from the home/building, like HVAC sound isolation mufflers.
If you don't do the outside walls and don't properly decouple them, then the drywall will vibrate those studs, which will send flaking noise up/down/out to everything those studs touch. Soundproofing with half measures is usually a waste of money. The good news is that when it's done right, it's a game changer. I can watch movies at reference level in the basement theater while my wife sleeps upstairs, and the theater room is also incredibly quiet. Its not a small amount of work though.

My build thread on AVS Forum: Nokomis Theater
  • floating double stud walls with a clip/channel ceiling
  • 2x 5/8" drywall walls and ceiling with Green Glue
  • 2x 5/8" drywall with green glue adhered to subfloor between the joists above theater
  • rockwool insulation filling every wall/ceiling gap
  • dual layer backer boxes on everything, sealed to the drywall with acoustic caulk
  • HVAC isolation mufflers on supply and return vents
  • 300+ lbs commercial studio soundproof door (STC 56)
 
anotherhobby said:
The two folks above that linked you to the theater building forum on AVS have sent you to the right place. Go there an ask your questions. I just finished (as in last week) building a soundproof room in my basement, and most of what I learned about the process I learned there. That forum is extremely helpful and very knowledgeable for building rooms like this.

Soundproofing is mass, damping, and decoupling. Sound is transmitted by waves vibrating the drywall, which vibrates the studs, when then vibrate everything attached to them (other studs, the drywall on the other side, the house framing, floors, etc). Those material vibrations are what you hear on the outside of any room when the door is closed.
  • More mass (more drywall) takes more energy to vibrate.
  • Damping (green glue) further reduces the vibration by converting it into heat between the layers of drywall.
  • Decoupling uses rubber bushings to float a whole studded wall (DC-04 clips) or to hang hat channel (RSIC-1 clips). It is also used to isolate other large objects from the home/building, like HVAC sound isolation mufflers.
If you don't do the outside walls and don't properly decouple them, then the drywall will vibrate those studs, which will send flaking noise up/down/out to everything those studs touch. Soundproofing with half measures is usually a waste of money. The good news is that when it's done right, it's a game changer. I can watch movies at reference level in the basement theater while my wife sleeps upstairs, and the theater room is also incredibly quiet. Its not a small amount of work though.

My build thread on AVS Forum: Nokomis Theater
  • floating double stud walls with a clip/channel ceiling
  • 2x 5/8" drywall walls and ceiling with Green Glue
  • 2x 5/8" drywall with green glue adhered to subfloor between the joists above theater
  • rockwool insulation filling every wall/ceiling gap
  • dual layer backer boxes on everything, sealed to the drywall with acoustic caulk
  • HVAC isolation mufflers on supply and return vents
  • 300+ lbs commercial studio soundproof door (STC 56)
Click to expand...
^^^THIS. All of it. Last year I did exactly with 2 exceptions. First is that my floor is concrete slab. It's now carpeted. Second it the door. I could get away with a solid interior door with seals. This isn't 100% soundproof but does a pretty good job. The sound path continues down a hall with 2 more doors before reaching the upstairs. That's enough to kill whatever gets past the room door, so no problems there. Finally, I too found AVS extremely helpful and I too got a great result. Good luck and cheers,

[EDIT: ps, I overordered green glue and have a case and a half left. I cqn give you a good deal on it but you pay shipping. PM me if interested.]
 
Thing to consider for construction practice: When soundproofing a basement it might create a moisture situation (especially wrt outside walls). One neighbor after creating a real quiet basement home theater (it was tightly sealed) ended up turning what appeared to be a relatively dry basement room into one with a serious mold problems. This was fixable retroactively but with a lot of extra cost.
 
keithm55 said:
Thing to consider for construction practice: When soundproofing a basement it might create a moisture situation (especially wrt outside walls). One neighbor after creating a real quiet basement home theater (it was tightly sealed) ended up turning what appeared to be a relatively dry basement room into one with a serious mold problems. This was fixable retroactively but with a lot of extra cost.
Click to expand...
That can be mitigated by making a room-within-a-room. My room has a 2' wide cavity at the ends allowing storage, access and promoting air circulation. That shaved off 4' from the length but it's very convenient for storing stuff like TV boxes. In addition, the side wall adjacent to the foundation isn't fixed to the foundation, there's a 3" gap. This also promotes air circulation and allows a fan if need be. Another benefit is that wires can be added retrofitted relatively easily. Thankfully my basement is amazingly dry and low humidity. The builder did an amazing job, but really I was just lucky. Cheers,
 
keithm55 said:
Thing to consider for construction practice: When soundproofing a basement it might create a moisture situation (especially wrt outside walls). One neighbor after creating a real quiet basement home theater (it was tightly sealed) ended up turning what appeared to be a relatively dry basement room into one with a serious mold problems. This was fixable retroactively but with a lot of extra cost.
Click to expand...
Mitigated a couple of ways for me:

1. Code required windows for egress and ventilation; the ventilation is an inlet duct for outside air and quiet fan and outlet duct, so the room has air circulation. That is invaluable for usage as well, gets way too hot and stuffy otherwise.

2. I just leave the door open when not in use so get some convective circulation with the rest of the basement air.
 
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