14 September 2017

Acoustical plenum barriers meet occupant expectations and comply with standards - Part 1

What are they and why do we need them now?

Author: Gary Madaras, PhD, Assoc. AIA, Rockfon Acoustics Specialist for North America

The use of acoustical plenum barriers is well established in some European and North American countries. The U.S. is only now realizing their optimal performance and cost benefits.

I keep hearing about plenum barriers, what are they?

Plenum barriers are tried and true sound-blocking devices used above suspended acoustical ceilings. They prevent distracting and annoying noises that are generated in one room, such as an office, from transmitting into other rooms through the open plenum above the ceiling. This plenum is formed when the interior partitions do not extend full-height up to the floor or roof above, but instead stop at the height of the suspended ceiling.

Plenum barriers are made of lightweight materials, such as semi-rigid, stone wool, insulation boards. They are only a few inches thick and have a foil facing on one side. They are oriented vertically and positioned directly over the interior partitions. The plenum barrier panels are abutted so they form a continuous barrier to sound, either along one side of the room, several sides or around the entire perimeter.

I haven't used them before, why do I need them now?

Occupant expectations, and acoustic standards, guidelines and building rating systems have become more stringent. When people enter a room and close the door, they expect acoustic privacy. A room with high acoustic privacy can look the same as a room with little or no privacy. This is the problem. The person does not know whether or not other people are overhearing private information.

Post-occupancy building surveys over the past 10 years clearly show that people are dissatisfied with the level of sound privacy that buildings provide. While they might not seek out the building's designer to complain directly, they are not satisfied and expect better.

Acoustic standards, guidelines and rating systems have become more widespread in their use during the past five years. These indicate a trend of requiring higher sound absorption and higher levels of sound blocking. For example, the WELL Building Standard requires a sound-blocking level (Noise Isolation Class) of 40 points between two adjacent offices. LEED version 4 requires a blocking level (Sound Transmission Class) of 45 points between standard offices. Four years ago, the WELL Building Standard did not exist and LEED did not have acoustic criteria for office spaces. The world is changing and so must our design practices.

In Part 2 of this three-part series, coming in October, the following questions will be answered:

  • Why can't I use the ceiling to block sound through the plenum?
  • Can I just use a full-height wall?

If you have questions about how to effectively use plenum barriers and ceiling systems for optimized acoustics, please visit or call us at 800-323-7164, email or click here to find a representative in your area.






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