Additional Mass Calculation

Let me preface this by saying...I'm sure this information is out here somewhere in a thread. If someone can just point me in the right direction I'd appreciate it. The Problem I'm getting too much sound leaking through the ceiling to the floor above. Current Ceiling Treatment

• Drywall decoupling using isolation clips attached to the studs (Quite Clips) and hat channels
• Two layers of 5/8" sheet rock with GreenGlue in between each layer.

What I Want to Know What benefit I can expect by adding another layer of 5/8" sheet rock + GreenGlue to the ceiling? Thanks in advance.

Do you have some pictures of the process that you took? Several things to look into. It could be your caulking job has either failed or it was not done properly to begin with. You could have, during the sheetrock install, jammed a few screws into the existing overhead joists which will bridge your mass and creating flanking. Also, to flanking, is the sound leakage coming from your recording room or from outside of it? If you have rooms overhead, flanking is always, always something that has to be monitored with much care, or you may end up with a situation similar to what you are suggesting.

Do you have some pictures of the process that you took? Several things to look into.

Unfortunately, I don't have any photos of the work in progress.

Also, to flanking, is the sound leakage coming from your recording room or from outside of it?

The recording room is below grade (ground), with concrete slab (foundation) behind three of the four vertical walls. It's possible that the sound is coming through the one wall that does not have foundation behind it, and up through that ceiling. but I think that's unlikely because that fourth, non-foundation wall, is also treated with isolation clips, channel hats and two layers of 5/8" sheetrock with greenglue, and cellulouse insulation. So I'm thinking it's the ceiling. Would I use a decibel meter to confirm the source? Thanks much for the reply!

That wouldn't help, much. If you can make sound and the meter can hear it and get a level on it, then you should be able to identify that with your own eyes/ears. But, if you use one and find that your levels are loud as hell, then you have to consider what the wall assembly has ability to stop. Your HVAC is as much an airborne path as an open window if you did not make the necessary baffles to protect against this. Pictures really really help. I have to go back to flanking but with the new information, that you have a thin wall, this could be your leakage area, your "weakest link". Maybe a simple sketch of what it is you have built would help me and others to get inside the room with you, so to speak. To add more mass on an already massed up ceiling, I don't think, initially this is the way to go. The problem has to be identified not covered up.

As vague as your query is with information, up to 10 dB in TL improvement in mid and high frequencies. Minimal change at the MAM resonance. Andre

Attached are two very rough sketches of the wall and ceiling construction in my practice space.

As you can see, the walls with foundation behind them do not use the isolation clips and the wall that does not have foundation behind it does use isolation clips

Whoops. One thing I forgot. The vertical wall with isolation clips also has cellulose insulation.

Is that an accurate representation of how you did your drywall joints between vertical and horizontal? If so, I'm wondering why you didn't stagger the joints? Also, did you seal all your layers totally airtight at each stage? How deep is the air cavity inside the walls / ceiling? Are yo absolutely certain that you did not accidentally drive a nail or screw where it could have bridged your isolation? In other words, a nail going through the ceiling drywall into the joists of the floor above? Even one single nail that does that would create a flanking path that could cost you isolation. Anyway, like Andre said, an extra layer of 5/8 drywall on the ceiling with green glue could buy you anywhere from nothing to around 10 dB additional isolation. Subjectively, 10 dB reduction is roughly half as loud. And it all depends on what TYPE of sound you are talking about. That extra layer would probably help lots if your problem is speech getting through, or practically nothing if it is low frequency impact noise. So the answer is "It all depends....". You didn't provide enough information to go on. But you also need to consider something else: Can your structure handle the extra mass? You can't just add another up there without checking on that with your structural engineer again! I'm assuming that you DID check with one before building that current ceiling? That's a lot of mass up there, hanging over your head... - Stuart -

Chris-P wrote:

As you can see, the walls with foundation behind them do not use the isolation clips and the wall that does not have foundation behind it does use isolation clips

So you have a wood framed wall with clips and hat track on it. If this is correct it is one of potentially several places that are plaguing you. Not only is it not a requirement but your transmission loss suffers in the low end. Which brings me to a question. When you are being disturbed by this noise, this sound leakage, is it low frequency, or something other than? I am leaning towards the wooden wall with clips that has a breach in the air cavity that is letting sound out, maybe it is somewhere aiming at the stair case that you use to get to this lower level. It's a guess... If your actual build is represented by your sketchup, then flanking is still in the picture aided by a broken mass/air/mass and I am not completely sold on your ceiling. Are there windows. doors anything else...a post maybe in the center of the room?

So you have a wood framed wall with clips and hat track on it. If this is correct it is one of potentially several places that are plaguing you. Not only is it not a requirement but your transmission loss suffers in the low end.

Why would clips and hat tracks be a detriment on a vertical wall and benefit on a ceiling? Educate me.

Which brings me to a question. When you are being disturbed by this noise, this sound leakage, is it low frequency, or something other than?

It's mostly low-end leakage from the kick drum.

I am leaning towards the wooden wall with clips that has a breach in the air cavity that is letting sound out, maybe it is somewhere aiming at the stair case that you use to get to this lower level.

You hit the nail on the head <pun/>. The wooden wall with the clips is facing a stair case. This wall also has a door on it. However, this door is not a standard six panel molded door. It has a solid core, threshold and rubber weather stripping to create a good seal. I also screwed two pieces of 2'x4' 1/2" MDF to the interior portion of the door with Green Glue between the two layers. The door is now pretty damn heavy. So I didn't think the door was the culprit. But I recently read some threads on this forum talking about the impact of a putting a traditional door knob in a "soundproofed" door. So I'm wondering if the door handle could be part of the problem. Attached is a photo of the wall in question. It was taken a couple weeks ago so it doesn't show the additional MDF sheets screwed into the door. I know this photo isn't super helpful. I'll take some more to show the room in its entirety. Also, there are no windows in the room. Thanks again for all the expertise. Much appreciated.

... threshold and rubber weather stripping to create a good seal.

A single seal on a door probably isn't enough, and ordinary weather strip also probably isn't doing a good job of creating a totally air-tight seal. You might want to add at least one more seal, maybe two more. Take a look at the doors section of Rod's book to see how it should be done. Also, I hope you beefed up your hinges on that door when you added the MDF. For that kind of mass, you need heavy duty hinges. You also didn't answer the question on the joint between wall sheetrock and ceiling sheetrock...

You also didn't answer the question on the joint between wall sheetrock and ceiling sheetrock...

Can you please explain what you mean by stagger the joints?

Chris-P wrote:

Which brings me to a question. When you are being disturbed by this noise, this sound leakage, is it low frequency, or something other than?

It's mostly low-end leakage from the kick drum.

Adding a layer and green glue will not help significantly with low end isolation. It is controlled by the MAM frequency of the wall structure Andre

Adding a layer and green glue will not help significantly with low end isolation. It is controlled by the MAM frequency of the wall structure

Besides tearing down walls and redesigning the space, are there any other practical options to reduce low end leakage?

did you do anything to beef up the mass in the upper floor? Rod

did you do anything to beef up the mass in the upper floor?

Unfortunately, no. The floor above was already finished off. So that was out of the question.

Can you please explain what you mean by stagger the joints?

This is the way that you seem to have done it (non-staggered): This is the way it should be done:

Unfortunately, no. The floor above was already finished off. So that was out of the question.

You still could have beefed it up in the manner recommended in many places on this forum: from below, between the joists, by cutting strips of drywall to fit in between the joists, holding them in place with nails / cleats, then carefully caulking all around for an air-tight seal, then doing another layer the same way, then installing final cleats to ensure that things stay in place. from your diagram, it looks like you must have had access to the joists and to the gaps between them, since you attached your isolation clips to the joists.

Besides tearing down walls and redesigning the space, are there any other practical options to reduce low end leakage?

My guess is that you don't need to tear down the entire room, just the ceiling. If you take off the drywall carefully, you can probably re-use it to beef up the floor as described above. However, as I mentioned before in a previous post, before doing anything further to that ceiling, you should get your structural engineer to check on what you are planning to do: You are going to attache a LOT of mass to the underside of that floor, and the joists might not be rated to take the extra load. I'm assuming that you did hire a structural engineer to check loads BEFORE you hung the new ceiling from those joists, right?

Chris-P wrote:

Why would clips and hat tracks be a detriment on a vertical wall and benefit on a ceiling? Educate me.

Chris, I do not do point by point comments, as a rule, they are just long and boring....but you may benefit. Thing is that if you built, had built or deemed that you needed to build a wooden framed wall, and it was not coupled in any way shape or fashion to the building then you wouldn't need clips. The reason is that the wood framing , if not coupled, is already, uncoupled from the structure. And that is what clips and hat track are used for. To decouple from an existing potential vibration bridge. That is why you did not need them. Specs suggest that these clips also do not have as good an ability in the low frequency. So you shot yourself in the foot there.

Chris-P wrote:

It's mostly low-end leakage from the kick drum.

And this is where you start feeling the loss of isolation, low frequency. Still, it may not be a direct result of using clips and track but more the potential hole, I am thinking, this wall backs up towards the staircase that may or may not have an adequate door behind this newly built wall with clips and hat track that you show. This is another breach in your mass/spring mass that allows low frequency out. Your ceiling in this area outside of the room, is there anything on the above joists? Is it sheet-rocked? With only one wall that is trying to stop your drums once the sound gets into the air space, it can move in the path of least resistance. That means that if there is not sufficient mass at least of the same type mass on the interior of this room, then sound can move directly up into this cavity. A simply overhead sheetrock ceiling is not enough!

Chris-P wrote:

You hit the nail on the head <pun/>. The wooden wall with the clips is facing a stair case. This wall also has a door on it. However, this door is not a standard six panel molded door. It has a solid core, threshold and rubber weather stripping to create a good seal. I also screwed two pieces of 2'x4' 1/2" MDF to the interior portion of the door with Green Glue between the two layers. The door is now pretty damn heavy. So I didn't think the door was the culprit. But I recently read some threads on this forum talking about the impact of a putting a traditional door knob in a "soundproofed" door. So I'm wondering if the door handle could be part of the problem.

The doorknob hole wouldn't be the problem if it were not on the problem side...so it isn't helping. Not that it is much of an issue, but it is a contributor to a cumulative process. I went through this whole ordeal with you to help you and anyone else that may view this latter the extreme importance of why there is a sticky, why the pertinent questions have to be asked and just how much "guessing" is involved when these specific helpful threads are not adhered to by those that think they do not apply to their unique issue. Look over your thread and look at the talent that is involved in this discussion. Those guys are basically "the guys"! But there still is not enough information due to lack of pictures, construction design history, what was used, built, how was it completed, etc, etc, etc to reach a definitive resolution to your concern I can say this, it has flaws, they are evident and until you get some hard visible information e.g pictures, this is a hunt and peck that no one should be asked to go through. Seals on your door not withstanding, what ever is behind that wall is in my guess, a breach in the airspace that is allowing the unobstructed passage of sound. It is not a true room in a room design and is failing you because of this shortcoming. It is failing due to incorrect install procedure and for the want of more mass, it is failing yet again. Rod brought up installing mass into the upper ceiling area. This would have been one of the most helpful things you could have done to get rid of the low frequency vibration. Mass is the thing that is used to make attempt to stop sound, and it is missing in a vital part of your isolation. It can be, as easy as the other things you and I have addressed, one of already several reasons why you are not getting the isolation in the low frequency area that you so badly wanted.

...by cutting strips of drywall to fit in between the joists, holding them in place with nails / cleats, then carefully caulking all around for an air-tight seal, then doing another layer the same way, then installing final cleats to ensure that things stay in place. from your diagram, it looks like you must have had access to the joists and to the gaps between them, since you attached your isolation clips to the joists.

This is a brilliant suggestion and would have been dead simple if only I had thought of it / found this forum prior to construction.

I'm assuming that you did hire a structural engineer to check loads BEFORE you hung the new ceiling from those joists, right?

Yes, I consulted with an engineer prior to hanging and the clips and hats should support the current load.

I went through this whole ordeal with you to help you and anyone else that may view this latter the extreme importance of why there is a sticky, why the pertinent questions have to be asked and just how much "guessing" is involved when these specific helpful threads are not adhered to by those that think they do not apply to their unique issue. Look over your thread and look at the talent that is involved in this discussion. Those guys are basically "the guys"! But there still is not enough information due to lack of pictures, construction design history, what was used, built, how was it completed, etc, etc, etc to reach a definitive resolution to your concern

It is now pretty obvious now that I made some rookie mistakes in designing and constructing this room. This was my first attempt at building an isolated space, so I suppose some mistakes were inevitable. I only wish I had discovered this forum earlier so I could have avoided some of the more substantial blunders. Hind sight 20/20 I suppose. I greatly appreciate the time that each of you has taken to answer my questions.

This is a brilliant suggestion and would have been dead simple if only I had thought of it / found this forum prior to construction.

You can still fix it, if you really do need that extra isolation. Yeah, it would be really sad to take off all that hard work on the ceiling and re-do it, but it probably would be worth it. It would also give you the opportunity to stagger the edges properly, and double-check for flanking paths in the ceiling. If you did that, plus trying to fix what xSpace suggested about the stairwell, plus the seals on the doors, then you probably could get a decent improvement in isolation. On the other hand, if you really want to do it right, you could take it all down and re-build it as a proper decoupled MSM room-in-a-room system, which would be much better. You might even be able to re-use a lot of the materials, if you take it all apart carefully. - Stuart -

You can still fix it, if you really do need that extra isolation. Yeah, it would be really sad to take off all that hard work on the ceiling and re-do it, but it probably would be worth it. It would also give you the opportunity to stagger the edges properly, and double-check for flanking paths in the ceiling. If you did that, plus trying to fix what xSpace suggested about the stairwell, plus the seals on the doors, then you probably could get a decent improvement in isolation. On the other hand, if you really want to do it right, you could take it all down and re-build it as a proper decoupled MSM room-in-a-room system, which would be much better. You might even be able to re-use a lot of the materials, if you take it all apart carefully.

The main thing I learned in this exercise is that continuing with this cold-war like approach to adding more and more mass to a flawed design will yield minimal isolation benefit and could be very expensive and possibly dangerous. :D I need some time to think through the different possibilities and formulate an approach. Thanks again to Soundmand2020 and xSpace.