Hot Tips: Acoustics

Controlling Noise In Classrooms

Acoustical performance is vital ceiling selection criteria for classrooms. The reason: students must be able to hear and understand their teacher if they are to learn.

In the past, acoustical ceilings offered either good sound absorption to decrease unwanted sound levels in a classroom, or good ceiling attenuation to block unwanted sound intrusion from adjacent classrooms or corridors, but not both absorption and blocking in the same ceiling.

Now, the science behind the ceiling is able to offer a new generation of acoustical ceiling panels that provide an ideal combination of sound absorption as denoted by their Noise Reduction Coefficient (NRC) and sound blocking as denoted by their Ceiling Attenuation Class (CAC) in the same panel.

The NRC indicates the ability of a ceiling to absorb sound. It is expressed as a number between 0.00 and 1.00, and indicates the percentage of sound it absorbs. An NRC of 0.60 means a ceiling absorbs 60 percent of the sound that strikes it. A ceiling with an NRC less than 0.60 is considered low-performance, one with an NRC of 0.70 or greater, high-performance.

The CAC indicates the ability of a ceiling to block sound in one space from passing up into the plenum and transmitting back down into an adjacent space that shares the same plenum. The higher the number, the better the ceiling acts as a sound barrier.

A ceiling with a CAC less than 25 is considered low-performance, one with a CAC of 35 or greater, high-performance.

Regardless of whether it’s new construction or renovation, the best solution for both reducing the level of sound in a classroom and limiting sound intrusion into it is an acoustical ceiling panel that combines an NRC of 0.70 or greater and a CAC of 35 or greater.

About the Author

Sean Browne is principal scientist - Global Acoustics for Armstrong Ceilings.