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How to sound proof home theater room ceiling - Page 2

post #31 of 77
I am relatively new to this forum, just really starting reading/research earlier this year in an attempt to plan and build my HT. The subject of sound isolation was probably the most vexing part of defining my build. The biggest question in my mind was what was the minimum I needed to do to achieve my goal? You could do the minimum of just using 1-2 sheets of drywall against your ceiling joists, to the gold standard of installing floating joists in a room within a room configuration, and plenty of options in between.

Without actually being able to LISTEN to the various configurations available, and lack of data for the lesser ones (so what if DD against the joist has an STC value of x, and clips/dd/gg has STC of y, what does that mean to me in terms of what is heard in the room above?). I chose to take the suggestions of the expert opinions of people like Ted to do all that I could within budget and mechanical limitations to mitigate the problem.

Looking at it from a purely "mechanical transmission" standpoint, placing drywall directly against the joists vs. using RSIC clips was a no brainer. Consider a 12' x 22' room for instance....you'd have a total of approx 3500 Sq in of contact surface area between the joist and drywall available for direct sound transmission (1.5" wide joist x 144" long x 16 joists). With RSIC clips (assuming around 1 sq in per clip), you'd have maybe 60-70 sq in total.

So, that was an easy decision. The bigger (and more expensive one) was what does using GG buy me over and above just clips, single drywall, DD or whatever combination thereof? Hard to say (because I haven't heard it yet) but I ended up choosing to go the extra mile for isolation.

Feel like I'm rambling a bit here, but I guess my point is that I came to the conclusion there are no calculations to me made, or test data to prove out/demonstrate your final sound isolation prior to it being done. If isolation is important to you, then you do all you can within your budget based on the expert advice available here.
post #32 of 77
Sound isolation really begins with your defining what you want to achieve ... and then usually backing off that requirement to meet budgetary constraints.

There are two sides to this coin. The outside in and inside out views. The inside out perspective is the more common: "I want to listen to my stuff loud and not raise the ire of spouse, children, neighbors and environmentalists". The outside in perspective says you want to listen to the entire dynamic range of a recording (22dB SPL to 105dbSPL at the listening position) without clipping, distortion, or permanent hearing loss.

Let's look at both of these and use, as a starting point, the value of 35 dBSPL as the typical ambient noise level in a quiet suburban home. Also the recommended best practice which says the objective is you do not want to raise the noise level in an adjacent space more than 3dB (a doubling of loudness).

So from the inside out view, if your ambient noise level is 35dB, we add 3dB to that and say our goal is 37dB. Taking the top of the dynamic range of 105dB and substracting 37dB from that, we come up with 68dB. In the simpliest form, your isolation efforts need to reduce sound transmission through the walls/floor/ceiling by 68dB. Again, in its most simple form, you're looking for an STC of 68dB. That's pretty substantial. [NOTE: STC is a poor metric in this case since STC only considers the 1/3 octaves centered at 125Hz through 4000Hz and further is a single weighted number representing that entire range. But, for simplicity's sake, it's what we have for now.]

The ouside in view, says we have an ambient noise floor of 35dB, the softest sound recorded on a sound track is 22dB. You need to achieve a >13dB reduction in ambient noise inside the room. By comparison, that looks pretty easy to do until you start to consider noise being transmitted into the room by HVAC system, equipment fans, projector fans, etc. When we look to certification bodies ... THX for example ... the concern is less on noise sources you can control (dishwasher, children bouncing balls off the floor above) and more directed to environmental noises you cannot control (airplanes, traffic, trains, etc.). These noises by the way are loud by comparison to ambient and therefore the >13dB number is very minimal. OK, so what happens if you don't get the noise floor in the room to <22dB?. Let's assume your speakers will produce 22dB at the listening position using 15 watts. To produce 25dB would require 30 watts, to produce 27dB would require 60 watts, to produce 30dB would require 120 watts, to produce 33dB would be 240 watts ... you can see where this is going. Do the same calculation at 105dB (top of dynamic range) and you'll see you need some really large amps and some very, very loud speakers ... you'll be chasing the volume control forever or facing discomfort and permanent hearing loss. Remember the inside out piece? Your STC requirements are no longer in the 70 range; but, way, way beyond that.

Keeping the room quiet not only improves the audio experience but also reduces what you need to do to avoid wasting all your wattage energizing the entire house.

Let's go back to the OPs original ... ceiling only ... question. Or other poster's do one wall questions. What affect will that have. In almost every case the answer is almost nothing and "you'll be disappointed in the result". Let's simply define "you'll be disappointed" and "almost nothing" as meaning "no perceived audible difference". At best this is a generality (glittering generality for those of you across the campus in J-School*) and specific answers can only be calculated on a structure by structure basis. How much of a difference will depend on the isolation technique used. A hard barrier will do little to nothing. A highly damped barrier will reduce total acoustic energy transfer but, by how much, is strictly case by case (a high damped barrier is converting kinetic energy to heat energy and heat energy is hard to hear). The disappointment in the results will come from sound flanking through places you never thought you had.

If you want to build a room with four isolated walls and a drop ceiling ... well, it is similar to building an aquarium with no bottom (ok, with a perforated screen for a bottom). Individual results will vary based upon the structure itself and methods of isolation. Your happiness with the result will depend entirely upon what you defined as your objective. Based upon my own experience...well, you're better off doing this right. Rooms are expensive (if not impossible) to fix later. Equipment, chairs, carpet ... easy to upgrade later.

I figure that's about 3 cents worth.

*J-School. Journalism School. Found on the left side of the campus sharing a building with the Political Science Department. Courses are taught by the Contemporary Fiction faculty from the English Department.
post #33 of 77
This post should be a sticky!
post #34 of 77
Dennis - great write-up. Put me in the camp as someone who was going down the path of fixing one wall. Here is my situation...

Home builder built dedicated HT room on second story above garage. Here are the four walls.

Wall 1: Shared with adjoining upstairs bonus room and contains a single door.
Wall 2: (attached to Wall 1) Other side is exterior of the house
Wall 3: 2-3 feet of attic space on the other side and then an exterior wall.
Wall 4: (attached to wall 1) 2-3 feet of attic space on the other side and then an exterior wall.
Ceiling: 2-5 feet of attic space above and then the roof.

I was planning on reworking Wall 1 with DD+GG and a solid-core door to help reduce sound transmission to the other parts of the house. I would hate to go through this process if I wouldn't hear any noticeable difference. With this one wall being the key barrier between the HT and the rest of the house, I thought it would help if I did DD+GG.

I probably have a flanking path issue where Wall 2 & 4 contact Wall 1. I may be able to remove those flanking paths, but that would be some additional tear-down and build back up.

Thoughts?

Robert
post #35 of 77
Good question Robert. Regarding Dennis' point about the reduced noise floor in the room, you'd have to treat all walls, floor and ceiling.

With specific respect to sound getting into the house, the answer is... "it depends." Treating the one wall will bring you some relief, but it's impossible to gauge if you will find it satisfactory. I suspect not, relative to the cost and effort.

Sound can flank in the floor right under your wall. And the floor system I assume is rigidly connected to the house. As well the ceiling and 2 side walls are connected either directly or nearly directly to the house.

Given these flanking pathways, I would recommend you to either do nothing or do everything.
post #36 of 77
Argh.... tough decisions! Yes, the floor system is your typical engineered i-beams spanning multiple rooms. My goal is to do as little demolition as possible in an already finished room while getting the maximum sound isolation. I have already conceded to not having the perfect reduced noise floor within the room.

Right now, that shared wall is your typical interior 2x4 house wall with one layer of drywall on each side and a hollow cavity, and the single door is a hollow core door.

I wish I could test this, but my assumption is there would be quite a noticeable difference taking down the HT side of the drywall, putting in insulation, adding whisper clips, and then DD+GG. Then replacing the hollow-core door with a solid core door using threshold/seal sound treatments. That *seems* like it would make a big difference.

Even if I did all the walls and somehow the ceiling, how would you address the floor? Do you just lay down Acousti-mat under everything?

BTW... I have spoken with John a couple times at the soundproofingcompany. You guys are a great resource for us DIYers!

Robert
post #37 of 77
The other option I thought of was to keep the room finished as-is, and then just install another layer of DD with GG. Would this method be more preferable to the one-wall approach?
post #38 of 77
Robert ... I understand budgetary constraints. I want a P51 D model Mustang. My bugdet won't tolerate it and owning a picture of one just won't cut it. Even just having 500 gallons of fuel for one doesn't really convey the experience.

You are better off doing something reasonable (like another layer of drywall and GG) to all walls (and doing something with the floor) than blowing the entire budget on one really good wall. In the process, you'll need to do something with recessed light fixtures if there are any.
post #39 of 77
Thanks Dennis, I think I am onto Plan C, or maybe D, I lost track...

The three big items factoring into my final decision....

1. Budget, as always.

2. I don't want to tear down the ceiling as I would have to deal with 16" of loose insulation that is sitting on top right now. What a mess to deal with and I would rather skip this step.

3. Interior space considerations... with a 14x18 room, I want to keep as much of that 14' as possible as I want to fit in the furniture without feeling crammed against the side walls.

I found the old GG 37 page thread and after reading that plus the advice above, here is my current thought:

1. Tear down all the 4 interior HT walls and install staggered studs making a 2x5 wall on each side. Use 5/8" Drywall + GG + 1/2" Drywall. This demolition is not that bad and the overall cost should be less versus whisper-clips and hat channels all around. Plus I save on interior space.

2. The door the builder put in is actually a double-swing, hollow-core door that is in the wrong place anyways. So I will move the door down the wall and at the same time make it a single solid core door.

3. For the ceiling, install GG + 1/2" Drywall on top of the existing ceiling.

4. For the floor, install GG + 1/2" OSB on top of the current OSB subfloor.

Fortunately, the builder did not install any canned lights, so I should be good there.

Is the above approach a good compromise for budget, demolition, and interior space?

Robert
post #40 of 77
Quote:
Originally Posted by Steve*MH View Post

For clarification sake; it seems from the articles on the website mentioned, that the main elements of soundproofing doesn't involve any special materials such as MLV or "special" insulation; but basically multiple layers of drywall and green glue. Regarding the ceiling; it looked like R-19 insulation is involved in all the scenarios mentioned, so I am good to go there. It seems the choice now is whether to put multiple layers of drywall inside the floor joists and on the subfloor itself (seems difficult) or add multiple layers in a traditional method attached to the bottom of the floor joists. I have 9' ceilings; so perhaps I can give up a couple of inches for additional drywall. To take it to the next level would involve channels and clips; not decided if I need that level of proofing and the differences it would make over just three layers of drywall and green glue. What I am considering now is applying the R-19 to the subfloor (inbetween the floor joists) - which would "compress" the R-19 and add to is sound diffusing nature - right? Then leave the option for multiple layers of drywall and green glue to sound proof the ceiling. This would leave a "gap between the ceiling and the insulation/subfloor for fishing wires etc. down the road. How does this sound - OK? Thanks for any input.

9' ceilings? You will get no sympathy from me and my 7'3" ceilings :P
post #41 of 77
Quote:
Originally Posted by Robert_S View Post


2. I don't want to tear down the ceiling as I would have to deal with 16" of loose insulation that is sitting on top right now. What a mess to deal with and I would rather skip this step.

Understandable.

1. Tear down all the 4 interior HT walls and install staggered studs making a 2x5 wall on each side.

http://www.soundproofingcompany.com/library/articles/staggered_stud_wall_construction/

Use 5/8" Drywall + GG + 1/2" Drywall. This demolition is not that bad and the overall cost should be less versus whisper-clips and hat channels all around. Plus I save on interior space.

Use 5/8". Almost same cost but desirably heavier.

2. The door the builder put in is actually a double-swing, hollow-core door that is in the wrong place anyways. So I will move the door down the wall and at the same time make it a single solid core door.

Interior solid core. You'll need to gasket or weatherstrip. In ant event this will still be the big weak link relative to the other wall / ceiling surfaces.

3. For the ceiling, install GG + 1/2" Drywall on top of the existing ceiling.

5/8" as before

4. For the floor, install GG + 1/2" OSB on top of the current OSB subfloor.

7/16" minimum. 3/4" much better

Fortunately, the builder did not install any canned lights, so I should be good there.

Is the above approach a good compromise for budget, demolition, and interior space?

Robert

What about ventilation? The #2 source of flanking.
post #42 of 77
I was looking at 5/8 " + 1/2" inch as this was something Dennis was recommending in the long GG thread from a few years back. I am not sure if this still is his current recommendation though. I can go either way.

Regarding ventilation, our house has a main AC unit in the attic with insulated flex ducting coming off a plenum for all the supply and return runs. Each run has it's own separate flex duct from the register/return to the plenum. From what I have read, this type of duct work is good for sound absorption. Is there something else I should do with this type of duct work?

Robert
post #43 of 77
Quote:
Originally Posted by Robert_S View Post

I was looking at 5/8 " + 1/2" inch as this was something Dennis was recommending in the long GG thread from a few years back. I am not sure if this still is his current recommendation though. I can go either way.

Regarding ventilation, our house has a main AC unit in the attic with insulated flex ducting coming off a plenum for all the supply and return runs. Each run has it's own separate flex duct from the register/return to the plenum. From what I have read, this type of duct work is good for sound absorption. Is there something else I should do with this type of duct work?

Robert

The standard now is 5/8" x2. More mass is better.
post #44 of 77
What Cathan said exactly.

Regarding ductwork. Flex is lightweight plastic. R5 fiberglass. What happens if you placed this material over a bullhorn? Nothing at all. Flex is only effective if placed in a contained area like this sofit:

post #45 of 77
I am so glad to come across this great thread. Thanks you Ted, Dennis and others.

I am just starting to do the ceiling in my HT room. I have a little over 7 ft. ceiling, that I am stuck with.......(basement set up).

Double 5/8, GG and isolution tape.

I have "read" that R13 should be used, as there is little soundproofing from it. I can us R30 or R 19 as suggested in above posts.......which is the way to go??

I posted a question as to THX Quite rock in another thread, but this seems like a better opportunity to get some good info..........the only info I find is from the manufacturer.


Thanks, Jack
post #46 of 77
Quote:
Originally Posted by Ted White View Post

What Cathan said exactly.

Regarding ductwork. Flex is lightweight plastic. R5 fiberglass. What happens if you placed this material over a bullhorn? Nothing at all. Flex is only effective if placed in a contained area like this sofit:


Thanks for the picture.Really helps on explaining the process.On those sound isolation clips.They look like those metal studs they use in commercial drywall.Seems you could use those and run them opposite of your wood joist and screw your drywall layer into them.
post #47 of 77
The clips are just little "claws" that hold the metal Drywall Furring Channel. Simple system that does a good job decoupling.

jvvjvv, you'll want some real decoupling on the framing, not foam tape.
post #48 of 77
Quote:
Originally Posted by Ted White View Post

I say these things because I've been saying them here since 1999. If you want significant sound isolation you cannot depend on a dropped ceiling. Another blanket statement because it's true.

I have nothing against Ted, Dennis, et al., and certainly value the advice they offer here with no expectation of compensation, but let's not forget that they have personal, commercial interest in this industry.

I don't have any doubt that their involvement here has put money in their pockets in some instances. I'd also venture to guess it has saved forum members money in the long run and/or improved their soundproofing/acoustics.

We all make a living (hopefully), but for most of us, HT is a preoccupation, not an occupation.

That is all.
post #49 of 77
Thanks Ted. How long of a run inside the sofit should I use for it to be effective?

Say I have 8" flex duct to run inside a sofit. Per your picture, I could build the sofit with 2-3" of space around the flex duct to run to the supply or return.

Another idea I had... how about if I made the sofit itself the air duct with the flex duct at one end, the sofit lined with 1" fiberglass, and then the register at the other end? This should also reduce the noise of the air flow as in a gun silencer-type design where you have a larger cavity for the air to flow through.

Robert
post #50 of 77
Ted......I have just a little over 7' ceiling..........(basement setting).....how much height loss is there with the clips and furring strips?

Also I "read" that you should only us R13 insulation.......I have room for up to R30. Which is best.

Thanks, Jack
post #51 of 77
Wow, I haven't visited the construction forum in quite some time. I must be bored.
Good to see the DIY spirit is still alive.
I've had a couple cocktails tonight, my room is out of commission video-wise as I sold my pj last Saturday and am awaiting a new one so forgive me if I seem a bit surly.
I'll be brief:
Ted and Dennis are big boys and certainly don't need me to weigh-in but anyone questioning their commitment or knowledge is a fool.
Both of these guys have offered tons of free, invaluable advice over the years.
To the OP and anyone else, make it easy on yourself, follow their advice and achieve success or do nothing and save yourself the futility borne of your ignorance.
It's really that simple. Trust me.
post #52 of 77
Quote:
Originally Posted by Robert_S View Post

Thanks Ted. How long of a run inside the sofit should I use for it to be effective?

Generally 15' is recommended, though we have no data that says one way or the other. The larger the cross sectional area of the soffit (wider+deeper) the soffit is the less length you'd need.

Say I have 8" flex duct to run inside a sofit. Per your picture, I could build the sofit with 2-3" of space around the flex duct to run to the supply or return.

Maybe 4" to accomodate R13 without compressing it


Another idea I had... how about if I made the sofit itself the air duct with the flex duct at one end, the sofit lined with 1" fiberglass, and then the register at the other end? This should also reduce the noise of the air flow as in a gun silencer-type design where you have a larger cavity for the air to flow through.

1" fiberglass is the problem. We'd like 3-4". In any event, the soffit is the air duct. Matters not if there's flex duct in there. Sound leaves the flex to interract with the insulation. Only air stays in the flex.

Robert


Quote:
Originally Posted by jvvjvv View Post

Ted......I have just a little over 7' ceiling..........(basement setting).....how much height loss is there with the clips and furring strips?

1 5/8", including the clip and Drywall Furring Channel.

Also I "read" that you should only us R13 insulation.......I have room for up to R30. Which is best.

R19 for ceilings, R13 for walls.

Thanks, Jack

Here's an image of a recessed clip application:
post #53 of 77
Noah .... and, your point is?
post #54 of 77
Quote:
Originally Posted by Dennis Erskine View Post

Noah .... and, your point is?

Just to remind everybody what interests are at play here.

I think the fact that we share common goals of furthering the art and science of home theater is enough reason to look past potential commercial gain.

Raise your hand if you take every bit of advice from your mechanic, though. Bueller? Bueller?
post #55 of 77
Quote:
Originally Posted by Noah View Post

Just to remind everybody what interests are at play here.

I think the fact that we share common goals of furthering the art and science of home theater is enough reason to look past potential commercial gain.

Raise your hand if you take every bit of advice from your mechanic, though. Bueller? Bueller?

Noah, isolation/soundproofing isn't like acoustic treatments in that there can be a perceived difference/preference in approaches. What has been suggested is the universally accepted methods, based on science. It's a question of is it quieter? yes/no? There is no maybe like "does it sound better?"

Nobody on the forum has a monopoly on anything recommended (with the possible exception of GG - but there are independent tests on that to warrant its use...or just don't use it)

I suppose what I am trying to say is that you're accusations appear to be rather unfounded/unjust. Advice was asked for an advice was given.

BTW - if my Mechanic tells me there is something wrong with the car I listen and have it fixed
post #56 of 77
Quote:
Originally Posted by Elill View Post

Noah, isolation/soundproofing isn't like acoustic treatments in that there can be a perceived difference/preference in approaches. What has been suggested is the universally accepted methods, based on science. It's a question of is it quieter? yes/no? There is no maybe like "does it sound better?"

Nobody on the forum has a monopoly on anything recommended (with the possible exception of GG - but there are independent tests on that to warrant its use...or just don't use it)

I suppose what I am trying to say is that you're accusations appear to be rather unfounded/unjust. Advice was asked for an advice was given.

BTW - if my Mechanic tells me there is something wrong with the car I listen and have it fixed

I haven't made any accusations.

I thank the many manfacturers, dealers, designers, and installers for offering their expertise here with no expectation of compensation. I just ask that we all keep in mind that they may benefit from time to time from either their exposure here or from recommending products and services that they may provide.

Does that affect the advice they give? I would like to think not, but I'll leave that question to be decided by each individual forum member in each individual context.
post #57 of 77
Quote:


I just ask that we all keep in mind that they may benefit from time to time from either their exposure here or from recommending products and services that they may provide.

It is exactly this kind of horse manure that causes me to reconsider any participation here. This is a DIY community. We are not a DIY business. We sell our professional expertise and intellectual property...here we're giving it away. It has cost me far more time and money to participate over these 10 years, than I've gained in the few clients who've come, directly or indirectly from these forums. If I had a royalty payment from everyone that has copied various concepts I've laid out on these forums, I'd be retired and living comfortably in a mountain home in Montana supporting Angel Flight in a jet.

You want some acoustic panels. Sorry can't sell 'em to you. Want a set of Genelec speakers, Runco projector, Meridian 810 projector, Aerial 20T's...sorry can't sell 'em to you. Want a custom STC50, 400 lb door, custom mill work ceiling. That I can do. Want a turnkey room including the construction...that I can do. This is largely a DIY community. My stated objective back in 1999 was to get people to understand that what they do to their room is far more important than the equipment they put in it. I have donated man months, if not years, in working parties getting accredited audio and video "best practices" published, developing certification exams to separate qualified home theater designers from the blue smoke buffoons calling themselves designers. I don't have the time or the interest in dealing with cheap shots from self righteous clowns willing to soak up the free advice provided by professionals and then provide nothing but criticism in return. You should be encouraging the participation of Todd Welti, Sean Olive, Terry Montlick, Eric Desart, Don Stewart, Paul Barton and others of that ilk who've come and gone or are fading away due to this kind of backhanded slap in the face (or just the time responding to nonsense). Right now you have Ted and I ... well Ted.

You want to start a campaign? Then go over the "hide behind the anonymity" dealers, manufacturers, distributors, suppliers and other industry involved participants in these forums that don't have the common decency to provide their real names and associations.
post #58 of 77
I think it is the balance of the contributions of those in the business and those that are pure hobbyists that make the AVSforum the best that it could be.

Dennis, Ted, All the guys who work for AVS, The dude from Value Electronics, The Engineers and Marketing types from the various manufacturers, The professional speaker designers, The dude from Monoprice requesting product ideas

Without their contributions this place wouldn't be nearly as robust.

Don't leave us Dennis.
post #59 of 77
It blows me away how people can carp.
post #60 of 77
Quote:
Originally Posted by Noah View Post

I haven't made any accusations.

Actually you used a broad rush to imply that Dennis and others could be steering people in the wrong direction to make a buck. You didn't come out and flatly accuse someone, but rather did so is a round about way. It was a rather dick thing to do if you ask me. Talk about biting the hand that feeds you.
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