HVAC Background Noise Level

STC ratings for floor-ceiling assemblies are also available from laboratory test results, can be harder to find, as they are harder and more expensive to test. An experienced acoustic consultant will be invaluable for finding accurate STC ratings for floor-ceiling assemblies. 

Multi-story schools will require close attention to sound transmission through floor-ceiling assemblies. Incorporate similar acoustical design strategies as with walls, increase mass and insulation, allow for air gaps to break vibration travel, and seal any penetrations.

When designing noisy spaces such as a music room, you may need to control sound transmission with breaks, so that the noise cannot travel through floors and walls. Breaks typically include double-stud walls, staggering the studs, or installing resilient channels or neoprene isolators to provide an air gap between the stud and drywall. 

It is important to control sound transmission through joints and penetrations from duct work, plumbing, electrical wiring, and other openings made in the walls, ceiling or floors. It is best to seal these penetrations with a non-hardening acoustic sealant. These sealants may also double as fire caulk—check that you meet local fire codes.   

The STC requirements apply to exterior walls as well as interior partitions (walls, ceiling and floor). Meeting the requirements usually requires insulation between interior common walls, double layers of gypsum or acoustical drywall on at least one side of the wall, air gaps between common walls, sound-rated doors, and sealants around penetrations and door openings. 

Obtaining STC ratings that are accurate typically require the assistance of an acoustics consultant. The ratings should be taken directly from laboratory tests and verified by a professional or modeling tool. Designers should be wary of information obtained from marketing materials (except for window STC from an acoustics window manufacturer, which are generally reliable). An acoustics consultant is the best person to determine the actual STC rating for a partition, especially an atypical one.

Running calculations for credit compliance is the safest strategy to take. Relying on measurements taken after construction can be risky, in case you fall short and need to make costly changes.

Measurements of STC values taken after construction must be based on ANSI standard S12.60-2002 section E5.1.

Calculations and lab STC ratings for credit compliance must be made based on ANSI standard S12.60-2002 section D2.4.