Soundproofing master thread - Page 81 - AVS Forum | Home Theater Discussions And Reviews
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post #2401 of 2428 Old 09-26-2017, 06:42 PM
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Quote:
Originally Posted by Mpoes12 View Post
The standard way is to use a sheet of plywood or OSB as the first layer. It's also good practice to increase the number of clips and space the channel closer together. There IS a weight limit for the clips and channel so you want to be sure you don't exceed it. I calculated that my 35lb projector was probably ok but very close to the limit so I added channel so that the area around he projector has 12" spaced channel and a few extra clips. The plywood then stiffens the structure and gives you something to screw into.

I do not suggest that doing the first layer with OSB or plywood is a good thing for the entire first layer. Theoretically it will degrade transmission loss performance and adds a lot of extra work and expense. However strategically placed is a good idea. This is an example.

If it's too late then you need to find your channel and screw directly into that. At least two large screws must pass through channel.


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Thanks @Mpoes12

My framing is still open and no drywall yet. If I understand you correctly, for the area where I plan to have the projector installed, my first layer that goes on the clip/channel should be plywood or OSB instead of drywall and for the rest of the ceiling, go with drywall for both layers as I was already planning to do. Did I get that right?



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post #2402 of 2428 Old 09-26-2017, 09:36 PM
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Thanks @Mpoes12

My framing is still open and no drywall yet. If I understand you correctly, for the area where I plan to have the projector installed, my first layer that goes on the clip/channel should be plywood or OSB instead of drywall and for the rest of the ceiling, go with drywall for both layers as I was already planning to do. Did I get that right?



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Yes that is correct. I used a single 4x8 sheet. The advantage is that it spreads the stronger piece over a larger area. You could probably get away with a 4x4 sheet. I was just trying to be extra cautious. My favorite projectors are all on the heavy side and I wanted to be prepared.


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post #2403 of 2428 Old 09-27-2017, 08:04 PM
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Hello

When attaching the second layer of drywall to ceilings and walls, should it be screwed into the channel using fine thread screws or attach it just to the first layer of drywall using laminator screws?

Thanks


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post #2404 of 2428 Old 09-27-2017, 08:39 PM
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Into the channel.
Example: my builders use a 25mm drywall screw for the first layer. Then applies GG to the second layer of plates and uses a 42mm screw on that one.
Important: do not use overly long screws. It heightens the danger of screwing through the channel and into wood beams behind them, which will totally negate the use of the channels.
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post #2405 of 2428 Old 09-27-2017, 10:06 PM
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Originally Posted by LydMekk View Post
Into the channel.
Example: my builders use a 25mm drywall screw for the first layer. Then applies GG to the second layer of plates and uses a 42mm screw on that one.
Important: do not use overly long screws. It heightens the danger of screwing through the channel and into wood beams behind them, which will totally negate the use of the channels.


Thank you @LydMekk for your quick response. I've noted the lengths of the drywall screws as well.


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post #2406 of 2428 Old 09-28-2017, 06:32 PM
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Originally Posted by LydMekk View Post
Into the channel.
Example: my builders use a 25mm drywall screw for the first layer. Then applies GG to the second layer of plates and uses a 42mm screw on that one.
Important: do not use overly long screws. It heightens the danger of screwing through the channel and into wood beams behind them, which will totally negate the use of the channels.

They actually tested the effect of short circuiting the channel with greenglue and found the negative impact to be minor. Certainly don't want to do it on purpose but it's not the end of the world.

It makes sense too. The problem is the screw transferring sound energy into the joist or stud. If the screw is now attached to a large heavily damped piece of drywall then much of that energy is being damped away before it can transfer to the stud or joist.


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post #2407 of 2428 Old 09-29-2017, 08:44 AM
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That made little sense. Short-circuiting with GG??
And who are "they"?

TL;DR: dont use too long screws.
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post #2408 of 2428 Old 09-29-2017, 11:57 AM
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Quote:
Originally Posted by LydMekk View Post
That made little sense. Short-circuiting with GG??
And who are "they"?

TL;DR: dont use too long screws.
The Green Glue company posted results of STC testing where two layers of drywall and GG were used with resilient channel. They apparently simulated the effects of short circuiting the resilient channel assembly and noted that with GG, there was not much effect. My take from that is that if you're using two layers of drywall and GG, resilient channel may be somewhat redundant. There are other good reasons to use resilient though..more related to the reliability of the drywall long terms from flex etc.

http://www.greengluecompany.com/site..._Channel_1.pdf

Those tests show that the Green Glue tests are also 6db better at noise reduction in the 60Hz range..something they push for marketing...

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post #2409 of 2428 Old 09-29-2017, 02:37 PM
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Quote:
Originally Posted by LydMekk View Post
That made little sense. Short-circuiting with GG??

And who are "they"?



TL;DR: dont use too long screws.


They is green glue and someone else already noted what they found. It makes perfect sense if you understood what I was trying to say. I'm sorry what I wrote wasn't clear.

I stand by what I said. Don't do it on purpose but with green glue it's been proven a minor problem.


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post #2410 of 2428 Old 10-03-2017, 08:03 AM
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Question: My mine is an older house with a wooden plank sub floor underneath the hardwood floor. Does this pose any special challenges for soundproofing the basement HT room?
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post #2411 of 2428 Old 10-03-2017, 01:45 PM
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Originally Posted by impreza276 View Post
Question: My mine is an older house with a wooden plank sub floor underneath the hardwood floor. Does this pose any special challenges for soundproofing the basement HT room?


It can create challenges that could negatively impact soundproofing. A few concerns are sound leakage and squeeking from those walking above.

http://www.soundproofingcompany.com/...oof-a-ceiling/



As long as you don't mind doing this, it should fix the problems. I certainly wouldn't rip up your floors over this.


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post #2412 of 2428 Old 10-03-2017, 04:15 PM
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Thanks. I was looking at that and wondering whether it would make a big difference to quietening sound entering the rooms above. If the extra drywall and green glue only addresses footfall coming from above then it's not worth it for me. The additional cost of green glue would be painful!
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post #2413 of 2428 Old 10-03-2017, 04:58 PM
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Thanks. I was looking at that and wondering whether it would make a big difference to quietening sound entering the rooms above. If the extra drywall and green glue only addresses footfall coming from above then it's not worth it for me. The additional cost of green glue would be painful!


It's primary benefit is footfall. It probably adds a few dB's of extra transmission loss but not a lot. My guess is that most folks would mitigate that benefit with typical flanking paths.


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post #2414 of 2428 Old 10-04-2017, 07:21 AM
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My house is ten years old and the area above my theater is our living room and kitchen. There is a sub floor with a engineered wood floor that squeaks in places. I hear the squeaks when walking above, but don't hear them below when I am down stairs. Now I do hear my kid running and playing, but I not done any soundproofing at all. I was just going to do insulation, clips, channel, DD and GG for my ceiling. I think that would be enough. One layer of drywall and green glue would do something between the joist, but as you said GG is not cheap.

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post #2415 of 2428 Old 10-04-2017, 11:29 AM
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Originally Posted by Ladeback View Post
My house is ten years old and the area above my theater is our living room and kitchen. There is a sub floor with a engineered wood floor that squeaks in places. I hear the squeaks when walking above, but don't hear them below when I am down stairs. Now I do hear my kid running and playing, but I not done any soundproofing at all. I was just going to do insulation, clips, channel, DD and GG for my ceiling. I think that would be enough. One layer of drywall and green glue would do something between the joist, but as you said GG is not cheap.

I guess I feel that in the grand scheme of things the green glue isn't that expensive. You don't have to do two layers between joists as shown. You can do just one layer. The effect isn't as great but not a huge issue.

You could use acoustic caulk instead of green glue if the only purpose is to lessen foot fall and reduce squeaks. It would likely have a similar effect. I'm not sure it's any cheaper per oz and the green glue is at least proven for this purpose.

I didn't find this method to add a lot of benefit. My dining room is above the theater and has carpet. I can't hear footfall but can hear the bass of kids jumping. My plan is to add a second layer of plywood to the floor with GreenGlue at a layer date when we change our the carpet. That and something like serenity Mat will have the same effect and more.



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Looking back a few pages and the issue of ridged ducts running through a room was addressed, but just to confirm is the conscious to use flex duct where the duct vents into the room? Also, would it be worth it to build a duct muffler or silencer between the take off and vent drops? The goal being to reduce the flanking noise from the theater into the rest of the duct work.

I have an existing ridged duct that vents into my unfinished basement, running parallel between the joists. I’m planning on having the vents in the room ceiling, no extra isolated soffit for the duct work, and I’m wondering if I should replace it with flex duct or do anything else when I extend it. If it makes a difference I’m planning on doing all the recommend techniques discussed in this thread – DD + GG, clips and channel, DD between floor joists, disconnect walls, etc.
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post #2417 of 2428 Old 10-05-2017, 05:08 AM
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Looking back a few pages and the issue of ridged ducts running through a room was addressed, but just to confirm is the conscious to use flex duct where the duct vents into the room? Also, would it be worth it to build a duct muffler or silencer between the take off and vent drops? The goal being to reduce the flanking noise from the theater into the rest of the duct work.

I have an existing ridged duct that vents into my unfinished basement, running parallel between the joists. I’m planning on having the vents in the room ceiling, no extra isolated soffit for the duct work, and I’m wondering if I should replace it with flex duct or do anything else when I extend it. If it makes a difference I’m planning on doing all the recommend techniques discussed in this thread – DD + GG, clips and channel, DD between floor joists, disconnect walls, etc.
My basement is unfinished as well, but I have no duct work feeding the it. I do have run that go through joist to the upstairs and was told this are ok, but if I bring ducts and venrs into the room I should build duct mufflers and use flex duct to do it. A recommend size was for it to be 14' to 15' long and 15"x15" in a double lined box with insulation around it, but that it could be built in the joist as well. If you contact the Soundproofing Company they have a SIM on how to build it and can be of great help on other things soundproofing.

http://www.soundproofingcompany.com

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Issue from my plan review with my city:

I have an existing walkup unfinished attic. The existing stair well as existing up is 37.5 wide with 5/8 drywall on exterior wall side and 1/2 on interior side. they want a 36" clear width for code. One wall is against the exterior wall. As I need to open this wall to do the construction they want that wall to become R-15 vs the R-13 as built

I have 1.5 inches to play with to isolate and insulate the wall. I can not do anything to the exterior at this time.

What is the most isolation for the smallest width on a 2X4 wall with R15 so I can keep my 36" clear

My best plan so far is to use rockwool to get my R15 and DD/GG on both walls, this would take 1-1.25" (1/2 vs 5/8) of the available 1.5" and leave me a little wiggle room for measuring 36" when inspected. Drywall cost is a wash +/- a few sheets and would add a requirement of ~200sqft of rockwool.

Any other 'system' I came up with would take 1.5 inches minimum. Plan reviewer said to add 1/2 of rigid foam to the wall to add R3 and drywall.
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Quote:
Originally Posted by BSHuff View Post
Issue from my plan review with my city:

I have an existing walkup unfinished attic. The existing stair well as existing up is 37.5 wide with 5/8 drywall on exterior wall side and 1/2 on interior side. they want a 36" clear width for code. One wall is against the exterior wall. As I need to open this wall to do the construction they want that wall to become R-15 vs the R-13 as built

I have 1.5 inches to play with to isolate and insulate the wall. I can not do anything to the exterior at this time.

What is the most isolation for the smallest width on a 2X4 wall with R15 so I can keep my 36" clear

My best plan so far is to use rockwool to get my R15 and DD/GG on both walls, this would take 1-1.25" (1/2 vs 5/8) of the available 1.5" and leave me a little wiggle room for measuring 36" when inspected. Drywall cost is a wash +/- a few sheets and would add a requirement of ~200sqft of rockwool.

Any other 'system' I came up with would take 1.5 inches minimum. Plan reviewer said to add 1/2 of rigid foam to the wall to add R3 and drywall.
So the walkup goes to your atic, I take it is were you are building your theater? Are you putting DD, GG, clips and channel in you theater? If so I would just put in plain R15 pink insulation and 5/8" drywall up in the stairwell. I have read here a lot that the Ruxol doesn't make much difference from the pink stuff, but not for sure.

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So the walkup goes to your atic, I take it is were you are building your theater? Are you putting DD, GG, clips and channel in you theater? If so I would just put in plain R15 pink insulation and 5/8" drywall up in the stairwell. I have read here a lot that the Ruxol doesn't make much difference from the pink stuff, but not for sure.
The walkup is the entrance to corridor the media room in the attic. 3 of the 4 walls in the room are to be double stud, and clips&hat on the ceiling - it has 3 different angles to play with. Had planned on clips/hat on the wall that includes the stairs, but now that I have to add additional insulation there that cramped the plans, and only gave me 1.5" to use. The stairs go under the media room, so wanted to condition them as much as I could while I was at it to keep that 'hall' as quiet as I could.

Found this evening R-15 fiberglass in 2X4 size, the Roxul was thought as it was R15 for 2X4 over the fiberglass. Looks like I will just R15 fiberglass and double as much as I can in that stairwell to maintain my 36" width for code.
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You could use acoustic caulk instead of green glue if the only purpose is to lessen foot fall and reduce squeaks. It would likely have a similar effect. I'm not sure it's any cheaper per oz and the green glue is at least proven for this purpose.
AC is a fraction of the cost of GG. $77 delivered from Home Depot, case of 12.

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post #2422 of 2428 Old 10-10-2017, 12:56 PM
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AC is a fraction of the cost of GG. $77 delivered from Home Depot, case of 12.

There you go! It is certainly cheaper. I decided to calculate the actual per oz price in each case and it does appear to be a good bit cheaper. 22 cents an oz vs 39 cents an oz roughly. I guess each person needs to decide if that difference in he grand scheme of things is worth it.



I do think it’s important to stress that while I feel that acoustic caulk and drywall will help reduce footfall since it adds mass and damping. I don’t think it is likely to be as good as green glue. If you have a choice, use green glue. I know tests comparing caulk to green glue were done and found to show caulk to be only marginally effective.


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post #2423 of 2428 Old 10-11-2017, 05:42 AM
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One possibility I considered was using using Quiet Glue and applying Green Glue or acoustic sealant around the perimeter of the board to contain the dripping. I'm playing safe though and sticking to Green Glue.
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One possibility I considered was using using Quiet Glue and applying Green Glue or acoustic sealant around the perimeter of the board to contain the dripping. I'm playing safe though and sticking to Green Glue.
Wise. If you've seen the post in my sig.... my experience with QuietGlue was very disappointing. Not in that thread, but I'll mention here that even 6 months after application I still had dripping issues using QG on vertical surfaces. Unbelievable. I have witnessed very minor vertical "shear" of the glue with GG by comparison, and that was only within a few days of application and an isolated section that posed some other challenges to begin with.

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Quote:
Originally Posted by BSHuff View Post
Issue from my plan review with my city:

I have an existing walkup unfinished attic. The existing stair well as existing up is 37.5 wide with 5/8 drywall on exterior wall side and 1/2 on interior side. they want a 36" clear width for code. One wall is against the exterior wall. As I need to open this wall to do the construction they want that wall to become R-15 vs the R-13 as built

I have 1.5 inches to play with to isolate and insulate the wall. I can not do anything to the exterior at this time.

What is the most isolation for the smallest width on a 2X4 wall with R15 so I can keep my 36" clear

My best plan so far is to use rockwool to get my R15 and DD/GG on both walls, this would take 1-1.25" (1/2 vs 5/8) of the available 1.5" and leave me a little wiggle room for measuring 36" when inspected. Drywall cost is a wash +/- a few sheets and would add a requirement of ~200sqft of rockwool.

Any other 'system' I came up with would take 1.5 inches minimum. Plan reviewer said to add 1/2 of rigid foam to the wall to add R3 and drywall.
So, I'm not sure I'm interpreting your post correctly. Have I got this right?:

  • Existing wall 2x4 stud with R13 insulation in wall
  • R13 must be brought up to R15
  • Finished wall clearance is 37-1/2" and that's with the R13/15 wall to one side
  • The wall side in question is an exterior wall
  • Drywall of the stairwell interior is 1/2" thick
  • Max room for improvement is 1-1/2" width
Based on that, my suggestions:
  1. Replace R13 insulation with R15 Rockwool Safe'n'Sound or Comfort series. The R15 is 3-1/2" wide. Provided your wall was built with standard 2x4's and not the engineered 2x4's, it will fit. The engineered 2x4's are sometimes 1/4" thinner all around.
  2. You could add 1 extra layer of drywall on that same wall with Green Glue. Then you're down to ~1" wiggle room in the stairwell.
  3. Slap a 5/8" layer of drywall + GG on the other (interior side) wall in the stairwell. You could possibly do 2x 1/2" sheets more with GG between layers, but I'd say it's prolly not worth it and you'll shrink your gap <36" because the GG takes up a small amount of room.
I wouldn't be too concerned with shoring up the stairwell with DD/GG unless you plan to seal it off on both ends. Otherwise, most sound will simply travel around your DD/GG efforts and negate them. At least if I've got the correct mental picture with your situation.

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post #2426 of 2428 Old 10-12-2017, 05:30 PM
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Quote:
Originally Posted by HT Geek View Post
So, I'm not sure I'm interpreting your post correctly. Have I got this right?:

  • Existing wall 2x4 stud with R13 insulation in wall
  • R13 must be brought up to R15
  • Finished wall clearance is 37-1/2" and that's with the R13/15 wall to one side
  • The wall side in question is an exterior wall
  • Drywall of the stairwell interior is 1/2" thick
  • Max room for improvement is 1-1/2" width
Based on that, my suggestions:
  1. Replace R13 insulation with R15 Rockwool Safe'n'Sound or Comfort series. The R15 is 3-1/2" wide. Provided your wall was built with standard 2x4's and not the engineered 2x4's, it will fit. The engineered 2x4's are sometimes 1/4" thinner all around.
  2. You could add 1 extra layer of drywall on that same wall with Green Glue. Then you're down to ~1" wiggle room in the stairwell.
  3. Slap a 5/8" layer of drywall + GG on the other (interior side) wall in the stairwell. You could possibly do 2x 1/2" sheets more with GG between layers, but I'd say it's prolly not worth it and you'll shrink your gap <36" because the GG takes up a small amount of room.
I wouldn't be too concerned with shoring up the stairwell with DD/GG unless you plan to seal it off on both ends. Otherwise, most sound will simply travel around your DD/GG efforts and negate them. At least if I've got the correct mental picture with your situation.
Your assumption list is correct. The stair well goes down to a 180 degree landing/turn at the bottom with a solid core/weatherstripped door (was unfinished/unconditioned space). I keep kicking back and forth leaving the top open with a stub wall -which I know is worse for sound vs sealing the wall off at the top with an additional door/wall but gobbles up ~4' 'room volume' space. My overall width is only 17' so adding that wall slices a lot of space out of the room especially with the way the vent ductwork for rest of house is run and the required landings for doors at tops of stairs.

The wall is conventional 2X4, and I located some R15 fiberglass for 2X4 walls I will likely use there, it is about 15% more than R13 by square feet, but ~$.15-17 less than rock wool.
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post #2427 of 2428 Old 10-15-2017, 09:45 AM
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For HVAC flex ducts, I have the option of R6 or R8 insulation levels. R6 is minimum by my code. Is there any benefit of going to the R8 ducting for soundproofing reasons? If I plan to insulate the chase with as much fiberglass as I can, is there having a little more thickness around the actual duct going to help at all?
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post #2428 of 2428 Old 10-17-2017, 07:10 PM
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Quote:
Originally Posted by BSHuff View Post
For HVAC flex ducts, I have the option of R6 or R8 insulation levels. R6 is minimum by my code. Is there any benefit of going to the R8 ducting for soundproofing reasons? If I plan to insulate the chase with as much fiberglass as I can, is there having a little more thickness around the actual duct going to help at all?

Flex duct isn’t soundproof. It leaks sound like a siv. The advantage of the R8 is for sound absorption reasons, not soundproofing reasons. The R8 would absorb reflected sound energy inside the duct to a lower frequency than the R6, but neither the R6 nor R8 will absorb much above 600hz if it’s not acoustic flex duct with a perforated lining.

For soundproofing you need to have that duct in a soundproof enclosure of some type. A lot of people use soffits. If the flex duct leaves the soundproof shell of the theater at all it will leak sound. The transmission loss through R8 fiberglass is only a few db’s.


Sent from my iPhone with a keyboard that predicts what I mean very poorly
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