office one shared wall

[mbaffo]

I can hear the guy in the office next to me talking on the phone.  I can understand his conversation quite clearly, although he is not loud.  How well would it work to put insulation in the dropped ceiling and ad an existing layer of SoundStop by Knight-Celotex AND an additional 5/8 layer of drywall on top of the EXISTING drywall of the shared wall.  Do I need absolutely need the airspace of adding furrings?  How much more STC is there with building a wall on top of the wall versus just making the wall thicker with drywall and the dampening of the Celotex product?

[supersoundproofing]

You need to check the Office page for the answers to some of these issues:
See
http://www.soundproofing.org/options_sound_control_for_windows.htm
BJ Nash

[mbaffo]

My office does not have a window. Did you even read my post?

[johnbergstromslc]

If you work in a 'typical' office, the problem is the ceiling.  Those suspended tiles don't block much sound and the partition separating your office from his doesn't continue all the way up to the ceiling - there is basically a gaping hole over your wall that the sound can jump across.  Since you can't really plug up the hole, try some MLV laid down on top of the suspended ceiling, with the seams and edges taped up.  That will help a lot.

[agtrojan]

Adding density to your shared wall will reduce airborne sound.  This can be accomplished by adding 2 layers of MLV with adhesive backing over the existing drywall.  Install the first layer across your wall parallelt to your floor then add the second layer perpendicular to the first.  The result will be a doubling of the sound reducing quality of your wall.  

It is important that you seal the seams of the vinyl and caulk around the perimeter to create an air tight seal between the vinyl and the drywall.  To finish your project, add another sheet of drywall or paint the MLV.

Click here for more info on the MLV:

http://www.soundproofing.org/infopages/flooring.htm

If the noise is traveling over the wall and through your ceiling tiles then you could add the MLV over the tiles as long as the support system will hold up the weight.  Another approach is to add Acoustic Cotton Fiber Insulation over the ceiling tiles to absorb and block sound.  It may reduce the sound up to 15 dB.

Take a look at the product spec for the Cotton insulation:

http://www.soundproofing.org/brochures/SSP%20Cotton%20Fiber%20Insulation.htm

[johnbergstromslc]

Skip the cotton.  Focus on filling/blocking the hole over your wall.

[agtrojan]

I don't see a description of a hole over the wall.  Am I missing something?

If the wall is treated by adding density then the weak point will be the ceiling.  Placing the cotton over the ceiling tiles will absorb sound traveling through the tiles.

If the ceiling structure can support the weight then adding one layer of MLV (1 lb/sq ft, 1/8" thick) will add 25 STC to the system.

[johnbergstromslc]

I assumed he works in a 'typical' office building, with steel trusses.  In those situations, they don't build the walls all the way up the floor deck of the next floor.  The walls only go up to the bottom of the steel trusses, leaving room for HVAC and wiring to be run overhead.  Then, a suspended ceiling is hung.  Not much isolation.  A layer of MLV would help, but extending/blocking off the partition all the way up to the next floor would help a lot more.

Complicating things is the fact that the wall was probably not sealed properly and there are lots of penetrations from his space to his neighbors.  

[joel]

Hello mbaffo,

All you describe in your solution below is a lot of work that will only tire you out and still not solve your problem.



Here's a suggestion that has been effective for many, many people with this same problem:



For the noise coming up and over the common wall through your drop ceiling add a layer of bonded cotton insulation directly on top of the ceiling acoustic tiles.  This material has a 1.15 NRC and adds 20+ STC.  And then for the noise coming through the walls add two layers of 1/8" thick (1Lb/ft2) MLV directly to existing wall and cover with 5/8" dry wall - this will add 40 STC to existing and only add 7/8" to the wall.  The MLV is available with a pressure sensitive adhesive back (PSA) for a peel-&-stick application.  When you add the dry wall do not screw through to studs, only into existing drywall behind the MLV layers.  Many people use a little contact cement sprayed on the surface of last layer of MLV to hold the dry wall in place as they screw it on.



For bonded cotton info see http://www.soundproofing.org/infopages/natural_fiber.htm



And for MLV see http://www.soundproofing.org/infopages/flooring.htm



As mentioned - this solution works well.

Joel