PBS-P100 calls for acoustical ceilings in open offices with minimum NRC 0.85 or, for tier one high performance, a minimum NRC of 0.90. For enclosed offices, it calls for acoustical ceilings with a minimum NRC of 0.60 or, for tier one high performance, a minimum NRC of 0.75.
The WELL Building standard v1 by the International WELL Building Institute (IWBI)—typically applied to commercial office buildings—features a comfort section that seeks to “create an indoor environment that is distraction-free, productive, and soothing.
Easy as 1-2-3
Based on proven acoustical engineering practices and extensive laboratory testing performed by the Optimized Acoustics Research Program between 2014 and 2018, the optimized acoustics design approach can be simplified to three steps:
- Select a ceiling system to optimize acoustic absorption.
- Where needed, use walls or plenum barriers to effectively optimize sound insulation or blocking between rooms.
- Ensure the background sound level is within the desired range (the testing results were also reported in the proceedings of InterNoise 2015 and 2018, NoiseCon 2016 and 2017, and Acoustics Week Canada 2015 to 2018).
This approach results in more than just good acoustics. It also complies with the standards and helps achieve the best possible sound experience.
Optimize acoustic absorption
With greater awareness of the impact noise has on everyone’s daily lives, it is unsurprising building standards and guidelines require high-performance acoustic absorption in normally occupied rooms and are evolving with ever more stringent requirements. Many now mandate the use of a high-NRC ceiling system to meet the necessary level of acoustic absorption. For the best results, this means focusing on the true strength of ceiling panels and other overhead systems. When a contiguous ceiling aesthetic is not desired, acoustic islands and baffles (discrete absorbing elements suspended freely in horizontal or vertical orientations above the space) can also provide the required amount of noise and reverberation control.
Acoustic absorption occurs when an architectural surface, such as a suspended ceiling, wall-mounted panels, or carpet, converts energy in sound waves into insignificant heat energy by means of friction inside the pores of the material. The more sound energy is absorbed by the surface, the less is reflected back into the room as noise, reverberation, echo, or flutter.
Acoustic ceiling panels are manufactured as fibrous, airy, porous, and lightweight products, usually 5 kg/m2 (1 psf) or less. Sound passes through the panel’s surface and is absorbed in the porous core.
Absorption performance is characterized by NRC and generally varies between 0 and 1—the higher, the better. NRC can be categorized as good (0.70), better (0.80), and best (0.90). If a space is normally occupied by people, the NRC of the ceiling should not be less than 0.70. The optimal NRC for less noisy and sensitive spaces like private offices is 0.70, while most standards require minimum NRC 0.90 in open offices (Figure 1).
In enclosed spaces, such as private offices and conference rooms, acoustic absorption will apply to the performance characteristics of the ceiling sound treatment, acoustic wall panels, and whether the floor has carpeting. As the amount of acoustic absorption increases inside a room, the reverberation time decreases. This improves speech intelligibility, allowing people to better understand each other, especially during conference calls using speaker phones.
In open spaces, such as offices, break rooms, and corridors, the acoustic ceiling takes on an even more important role because there are no walls with acoustic panels. As the amount of acoustic absorption is increased in open spaces and corridors, the distance noise travels decreases. The buildup of sound pressure is prevented, fewer people are disturbed, and speech privacy improves.
One way to optimize acoustic absorption inside enclosed rooms or in open spaces is to use high-performing, sound-absorbing, suspended acoustic stone wool ceiling panels, islands, or baffles.