Soundproofing my basement

[Sanyobusiness]

I have owned several homes with basements and actually finished two of them.

If I understand what you are working with...the blower to the HVAC unit is in the basement and all of the ductwork for this unit is in between the floor joists. Sound is traveling to the upper floor via "vents"...do you mean ductwork or air registers?

Ductwork. There are no registers in the basement, so a large part of the sound problem is noise is getting through the duct walls and bouncing up the ducts/vents and out the registers in rooms. On a quiet night, you can pretty easily listen in on conversations in the basement. Jamming out to records, even with the volume turned down to a respectable nighttime level—might as well have a speaker right inside the registers in each bedroom.

It seemed to me that a large part of the issue could be solved by stopping sounds from getting into the vents, either with some kind of foam/fiberglass insulation batting, possibly followed by an additional layer of tin on the outside. Of course, this is just my "it would probably work" theorizing. I thought by asking here, I'd find out which product or technique to use, and which to avoid. Not so easily done, apparently.

Additionally, the ducts in the basement don't actually go between the joists, they hang just below them. Would be nice if they had been fitted between joists as I think that would make solving the issue that much easier. There are no beds on the first floor above the basement, and with carpeting and what not, I don't think there is so much getting through that way regardless. Also, there is a large "main duct" going longways along the center of the basement which is (roughly, I'm at work now so just guessing) 8-10" tall, maybe 16" wide, and 20ft long or so, which all the smaller ducts come off of and run to their particular sections of the house. Seems like this large rectangular walled duct is more likely to vibrate like a drum, rather than reflect sound like the round ducts would. Again, just armchair theorizing.

Duct work insulation is something you can buy at the local big box hardware store. If you meant sound is coming thru the air registers...I'm not real sure what can be done.

Just as a general thought...cosmetically this is not the best option but you might be able to just attach some insulation directly to the ceiling joists to give you a sound buffer.

Concrete/cinder block walls...In my 1st home, I didn't have a lot of cash...one contractor at a time, I paid professionals for HVAC (heat pump), electrical, plumbing the bath, installing a sump pump...also the tile floor. Everything else I did myself to save money.

You don't need a ton of insultation here...I used 2 x 2 stock attached them directly to the concrete wall 16" on center and filled space in 1.5" foamboard type insulation. I left it in this state for nearly 6 mos...I eventually drywalled all the walls and the ceiling.

Tax man cometh...I asked each of the subs did I need a building permit...they all said we'll do everything to code, but only if you want to pay taxes on this newly heated space.

That's the thing... heat radiating off the ducts warms the basement fairly well. Doesn't really need vents in the basement. So by solving this problem, I'll be creating a new one. Making my basement colder!

 

[2channel lover]

Ductwork. There are no registers in the basement, so a large part of the sound problem is noise is getting through the duct walls and bouncing up the ducts/vents and out the registers in rooms. On a quiet night, you can pretty easily listen in on conversations in the basement. Jamming out to records, even with the volume turned down to a respectable nighttime level—might as well have a speaker right inside the registers in each bedroom.

It seemed to me that a large part of the issue could be solved by stopping sounds from getting into the vents, either with some kind of foam/fiberglass insulation batting, possibly followed by an additional layer of tin on the outside. Of course, this is just my "it would probably work" theorizing. I thought by asking here, I'd find out which product or technique to use, and which to avoid. Not so easily done, apparently.

Additionally, the ducts in the basement don't actually go between the joists, they hang just below them. Would be nice if they had been fitted between joists as I think that would make solving the issue that much easier. There are no beds on the first floor above the basement, and with carpeting and what not, I don't think there is so much getting through that way regardless. Also, there is a large "main duct" going longways along the center of the basement which is (roughly, I'm at work now so just guessing) 8-10" tall, maybe 16" wide, and 20ft long or so, which all the smaller ducts come off of and run to their particular sections of the house. Seems like this large rectangular walled duct is more likely to vibrate like a drum, rather than reflect sound like the round ducts would. Again, just armchair theorizing.



That's the thing... heat radiating off the ducts warms the basement fairly well. Doesn't really need vents in the basement. So by solving this problem, I'll be creating a new one. Making my basement colder!

Well...you've painted a more complete picture now...I can visualize the space a bit better. I don't need to tell you this, but you're kind of in pickle here.

If jamming to records in the basement is a pastime for you...you need to fix it, because as is, you're compromising on more than one end here. You don't get to enjoy your music at a volume that you maybe you might like. Secondly, the people in the bedrooms may not want to hear music at all.

Your best bet is something I don't think you want to do, but the earlier suggestion of a drop ceiling with acoustical panels is probably the best solution....yes, you will lose the radiant heat factor, but you have power...an electric floor heater is not the worst thing.

 

[Matthew J Poes]

Ductwork. There are no registers in the basement, so a large part of the sound problem is noise is getting through the duct walls and bouncing up the ducts/vents and out the registers in rooms. On a quiet night, you can pretty easily listen in on conversations in the basement. Jamming out to records, even with the volume turned down to a respectable nighttime level—might as well have a speaker right inside the registers in each bedroom.

It seemed to me that a large part of the issue could be solved by stopping sounds from getting into the vents, either with some kind of foam/fiberglass insulation batting, possibly followed by an additional layer of tin on the outside. Of course, this is just my "it would probably work" theorizing. I thought by asking here, I'd find out which product or technique to use, and which to avoid. Not so easily done, apparently.

Additionally, the ducts in the basement don't actually go between the joists, they hang just below them. Would be nice if they had been fitted between joists as I think that would make solving the issue that much easier. There are no beds on the first floor above the basement, and with carpeting and what not, I don't think there is so much getting through that way regardless. Also, there is a large "main duct" going longways along the center of the basement which is (roughly, I'm at work now so just guessing) 8-10" tall, maybe 16" wide, and 20ft long or so, which all the smaller ducts come off of and run to their particular sections of the house. Seems like this large rectangular walled duct is more likely to vibrate like a drum, rather than reflect sound like the round ducts would. Again, just armchair theorizing.



That's the thing... heat radiating off the ducts warms the basement fairly well. Doesn't really need vents in the basement. So by solving this problem, I'll be creating a new one. Making my basement colder!

Sorry I didn’t read this carefully and gave you bad advice. Sounds like sound coming through the walls of the duct are your main issue?

If that’s true I would consider two options:

First is damping the outside of the steel duct with a damping compound. Such as:
https://www.quietrock.com/products/quietcoat

Second is wrapping with an MLV and fiberglass wrap like this:
https://www.tmsoundproofing.com/Noise-Damping-Pipe-and-Duct-Wrap-MLV-Fiberglass.html
This will add as much STC to the ducts as you could need before needing to actually finish the basement. Without finishing the basement there is no way to add much isolation.

The material costs are high but the labor is far more minimal than other options. It’s also a solution that gives you room to grow.

You should check to make sure there are no duct openings in the basement. My furnace, for example, has a vented cover that provide an opening to the ducts. If it wasn’t in a finished and closed-off space it would provide significant sound leakage. Even just 1mm of gap into the ducts will allow significant (read most) sound to enter.