By Gary Madaras, Ph.D.
Suspended acoustic ceilings are mainstream inside many types of buildings and can serve multiple sound-related roles. They often are used primarily to add sound absorption high in the room where it is most effective (A in Figure 1). If the partitions between rooms do not extend full height, ceilings can be combined with lightweight plenum barriers to provide privacy from adjacent rooms on the same floor (B in Figure 1). Along with the floor slab, ceilings can provide sound isolation from rooms on the floor above (C in Figure 1). Lastly, suspended acoustic ceilings can be the only noise attenuation device between mechanical units in the plenum and occupants in the rooms below (D in Figure 1).
The designer and specifier decide which of these roles the ceiling will take in any project. The ceiling can assume all, none, or any combination of the four roles. It is possible for the partitions and floor slab to provide adequate isolation without a ceiling. Mechanical equipment can be located remotely to sound-sensitive rooms. Absorption can be provided on other surfaces and via furnishing. Therefore, it is important to establish if a ceiling will be implemented into the design and which roles it will take, so the other components of the building can be designed and specified appropriately.
Prior to 2015, there was not a lot of information available to design and specification professionals on the performance of modular, suspended, acoustic panel ceiling systems inside commercial buildings, especially when they are combined with floor slabs, plenum barriers, light fixtures, and air distribution terminals and units. As a result, some designers and specifiers have had to rely on rules of thumb or misapply certain acoustic metrics to situations for which they were never intended. This article discusses systematically each potential role of acoustic ceilings, how ceilings work with other essential building components, and how specifiers can adjust their specifications for improved results. References to other articles written by the author will be provided for an expanded understanding of each topic.
First role: Room acoustics
Most occupied rooms and spaces require sound-absorptive surfaces to function properly. Adding absorption can make speech intelligible in learning spaces, create comfort by lowering occupant noise levels in restaurants, increase privacy in office workplaces, and improve patient outcomes by creating a quiet healing environment. The ceiling is the most effective surface for adding the required sound absorption because it is a no-contact surface and exposed to the sound field more than the floor and walls are.
The Canadian Standards Association (CSA Group) Z412 Office Ergonomics – An Application Standard for Workplace Ergonomics requires a minimum ceiling noise reduction coefficient (NRC) of 0.95 in unpartitioned open offices.1 ANSI/GBI 01-2019, otherwise known as Green Globes, requires minimum ceiling NRC of 0.90 in open offices, patient and eldercare areas, medication safety zones in healthcare facilities, and exam and treatment rooms in medical office buildings.2 The WELL Building Standard (WELL) by the International WELL Building Institute requires the ceilings over open workspaces and conferencing, learning, and dining spaces to be NRC 0.90.3 WELL claims that compliance with this high NRC criterion improves the functioning of the cardiovascular, endocrine, and nervous systems of the building’s occupants.
