Hot Tips: Acoustics
Controlling Noise In Classrooms
- By Sean Browne
- May 1st, 2016
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
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.
This article originally appeared in the May 2016 issue of School Planning & Management.
Sean Browne is principal scientist - Global Acoustics for Armstrong Ceilings.