Speech/Noise Isolation In Commercial Building

[Yeldud]

We are specifying design build criteria for fitup of some temporary (10 years or less) 2nd floor tenant space in a two story commercial building. The tenant has Interview, Polygraph, and Conference Rooms which require speech privacy. For these areas, Architect is specifying a minimum 56 STC rating separation from adjacent spaces using floor to floor walls with double 5/8" gyp board on metal studs with 3" blanket insulation and all joints and openings sealed etc. Also is calling for door assemblies to meet this same rating, and expects HVAC supply and return ductwork to not compromise this rating. From what I can gather this single number STC rating is an extremely agressive goal to achieve with conventional sheet rock and stud construction, and with hvac silencers etc. and may not be a realistic way to define the required noise isolation to provide speech privacy (the goal). I've seen some information indicating STC 45 might be more realistic, but not sure where i might find more guidance on what to specify for a target noise reduction. Any advice would be appreciated. Thanks, Yeldud

 

[MikeyP]

If you have usenet newsgroup access try posting your question in the alt.sci.physics.acoustics group. There are a number of building acoustics experts with practical experience there who should be able to help you.

M

 

[Yeldud]

MikeyP - thanks for the tip. I'm not familiar w/ Usenet but will look into it. thanks again. Yeldud

 

[DRubio]

Under ideal test conditions STC 56 could be achieved with the construction described below (sounds similar to what you described):

Wall should be full height
2 layers 5/8" GWB
3-5/8" 25-gauge metal studs
R-11 batt insultation in cavity
2 layers 5/8" GWB

In the field results will most likely vary somewhat.

The door could possibly be an acoustical weak link. Pemko and Krieger have specialty door products such as gaskets and astragals (as well as doors) that might help maintain the desired rating.

Note: a lower gauge metal stud could potentially reduce the STC rating.

Also, the design for speech privacy will have dependancies on the characteristics of the source and receiving spaces. It could be possible that some walls may need a slightly higher rating while others do not.

 

[DanT]

The ASHRAE handbooks have excellent plainly written sections on noise and vibration control.

Architectural graphics Standards (6th edition ~ 1970) bases their criteria on the type of occupancy >>and<< the adjacent area.
Confidential privacy areas adjacent to a manufacturing area or mechanical room would require STC 52.

Did your construction specs include Resilient mounting on at least one side? It's easily done with specially shaped commercial steel strapping AND SHORT DRYWALL SCREWS. I'd recommend it. Our first floor ceiling is single layer Gypsum mounted on steel strapping with mesh sides. Our bedroom has ended up on the first floor below our teen age daughter's carpeted bedroom. We hear body slams but no voices and no foot steps. Her music has to be pretty darned loud to disturb my sleep.

The crew that installs the drywall must understand that the screws MUST be allowed to hit the studs, as that will short circuit the channel. If they think they can use long screws and mark the floor or Eye-ball the studs and miss them they are dreaming. Before they bid on the job they need to know about the short screws, and the importance of ZERO short circuits, and that there must be an inpection after the first side is finished.

Various flanking details can ruin a good installation.
Duct interiors need to be lined on all surfaces with at least an inch of fluff for at least 10 feet. MOre is
better.