Shared wall = shared noise

[Esoteric]

Okay guys, so I have a client with the back wall of their main worship center being a shared wall with the side wall of their Children's worship area. I told them there would be issues when I surveyed for the lighting and video install. The GC said that putting insulation in the wall would be enough. Guess what. It wasn't.

So anyone have any ideas for more soundproofing in this situation?

It is a double thickness wall with standard insulation in both sides.

Mike

[sadlerjon]

Do you know how the stud cavity is structured? Is it a set of offset studs, or are they connected to each other via direct contact or contact with an intermediate surface?

Also, does the wall extend completely above the finished ceiling? If so, what sort of material is top of the stud wall anchored into? And what sort of penetrations exist through the wall for plumbing, HVAC or electrical?

Is there any possibility of being able to rebuild one side of the wall?

[Esoteric]

The walls are in direct contact, the studs are, I believe offset (I did the install over a year ago, I forget).

The drywall goes all the way to the ceiling in one area and stops about 12' off the floor (leaving 2' with no drywall) in another. The top is the internal ceiling insulation (it is a steel building, old roller rink, shed type thing). There are no penetrations in the wall where it exists (everything goes out through the unfinished portion).

That depends on their budget, but I would say 98% no.

Just fyi we run about 110db on one side of the wall (HEAVY on drums and percussion), which is the main worship center side with the sound going right at the the shared wall. The other side runs about 85db with all the sound going away from the shared wall, but the kids scream at who knows what db towards the shared wall.

Mike

[tedanderson]

Build another wall in front of the existing wall with about 4-6 inches of space between them.

The idea is to create a system where the sound is absorbed, reflected and dissipated for each layer. Building up the thickness on a wall still transfers most of the sound but when you have a gap between two walls, that energy is dissipated after going through the first wall and then it's reduced even more as it has to go through a second wall. It's much like how a bullet can easily go through a solid piece of steel but if you shoot through 3 or 4 mattresses, the bullet will get stopped.

[Esoteric]

Yeah, I understand the science behind it, but I don't think building a new wall is going to be in their budget. Any other ideas?

Mike

[[Director] Joseph B]

Sue the contractor who said it was sufficient after he was warned it wouldn't be.
His lack of competence should not be your problem.

[Brad Weber]

Without doing any analysis, my guess is that with the levels and frequency range involved, you probably won't get the desired isolation with the existing basic wall construction. You could add more sheetrock on each side but that will provide minimal gains at this point. You cold reattach the sheetrock with resilient channels on the Sanctuary side but that would seem to be major reconstruction and has to be implemented properly or it can actually make things worse. You could rebuild the facings using thicker or denser materials and products like Green Glue. However, getting you where you want may take something more like a double studs with separate runners or masonry base wall construction.

However, that doesn't mean you can't get some improvement. The first step is usually to make sure you are getting the most of what they already have. The sheetrock needs to go to the deck above and by that I mean to a hard surface where it can be sealed airtight. The same at the bottom and corners as any gaps provide a flanking path. While there may not be obvious penetrations, what about things like back-to-back receptacles? And might there be conduit, piping or even intentional bridging inside the wall that defeats the potential benefit of offset studs by providing a solid path from one leaf of the wall to the other?

[Esoteric]

Now that I look at my notes there are several gaps in place. There is the huge gap in the wall between the audio/video electrical room and the childrens area (the wall is unfinished above the 9' drop ceiling). There are 3 air conditioning vents on the back wall. There are the conduit holes in the electrical room, and a 3" PVC pipe that runs into the wall behind the booth. On the children's side there is also a hole for an audio panel and the wall is unfinished 6" from the roofline. Also the wall is unfinished above the drop ceiling in rooms 122 and 123.

So there are lots of gaps.

But you think Brad that possibly because of the frequencies that anything other than major construction is not going to do much good?

Mike

[Esoteric]

I wish they would. This GC was terrible (between tiles that are coming up, doors that leak, etc). So was the electrical contractor who blew up part of my dimmer rack (not to mention broken electrical outlets). But for some reason this church is not one to file suit or even threaten in order to make people fix their mistakes.

Mike

[cmchamp]

Unfortunately, the holes need to be plugged, the wall may need to be deconstructed and constructed properly. Either the architect didn't know what they were doing and improperly designed the wall, drew it wrong, or the contractor is simply doing what the plans say.
Without seeing a detail of that wall, I can't say what the issue was.
I have at home several drawings of proper high STC construction, and it's also available in a Google™ or YaHoo!™ search.
Who-ever was their church planning consultant did a bang up job messing them up by thinking they could put two worship spaces back to back with a gypsum board wall in between.
C.

[sadlerjon]

Here's a picture of different types of wall construction and the increasing sound isolation that comes with them.

http://forum.ecoustics.com/bbs/messa...579/128703.jpg

And as mentioned by others, the wall needs to be tight with no essentially no penetrations and go all the way to the hard deck above to be effective.

[Brad Weber]

Originally Posted by Joseph B

Sue the contractor who said it was sufficient after he was warned it wouldn't be.
His lack of competence should not be your problem.

I guess I interpret it differently as I read it to be that Mike told the Church that he believed they would have a problem with the wall when he was on site. I don't see where it was stated that the Contractor stated it was sufficient, or where any specific basis or criteria for doing so was defined, or where the Contractor was even necessarily informed of any perceived deficiency. A common problem is that something like this simply does not get addressed when it should or other considerations, such as construction cost, take priority and drive decisions without necessarily considering, or maybe even with considering, the potential impact.

I am going through a similar situation right now where trying to reduce the overall construction costs for a Chapel introduced a noise isolation condition that will be difficult and expensive to fix. This aspect was simply not considered by the anyone involved at that time when making the decisions that led to this situation. This is actually quite common, sometimes what seems to be advantageous has negative implications that aren't readily apparent to everyone.

Anyways, I would hesitate to blame anyone or question their competence in a public forum unless I know that what they did conflicts with what was requested from them and that they were truly negligent.