noise reduction coefficient

8/10/2019 Noise Reduction Coefficient

1/3

What is an NRC?

NRC stands for Noise Reduction Coefficient. The method by which NRC is ultimately obtained can be:the Reverberation Room Method (ASTM C423) or the Impedance Tube Method (ASTM C384). TheReverberation Room Method is the more popular of the two in terms of tests conducted on acousticalroom treatments. How this method works: Approximately 72 square feet (or more, but not less) ofmaterial is placed on the floor of a Reverberation Chamber - a big room with (usually) all hard,concrete surfaces (the opposite of an ''Anechoic'' Chamber - a room with no echoes) - and the changein absorption from the empty room to the room with the treatment area on the floor is measured. Akind of ''Before and After'' test.

NRC Noise Reduction Coefficients

The Noise Reduction Coefficient (NRC) is a scalar representation of the amount of sound energyabsorbed upon striking a particular surface. An NRC of 0 indicates perfect reflection; an NRC of 1indicates perfect absorption. In particular, it is the average of four sound absorption coefficients of theparticular surface at frequencies of 250 Hz, 500 Hz, 1000 Hz, and 2000 Hz. These frequenciesencompass the fundamental frequencies and first few overtones of typical human speech, and,therefore, the NRC provides a decent and simple quantification of how well the particular surface willabsorb the human voice. A more broad frequency range should be considered for applications such asmusic or controlling mechanical noise.

Acoustical materials manufacturers often report NRC values higher than 1.0 due to the way thenumber is calculated in a laboratory. A test material's area does not include the sides of the panel(which are exposed to the test chamber) which vary due to its thickness. A certain percentage of thesound will be absorbed by the side of the panel due to diffraction effects.

Noise Reduction Coefficients (NRC) for Common Building Materials:

Material NRC Brick, painted .00 - .02 Brick, unpainted .00 - .05


2/3

Carpet, indoor-outdoor .15 - .20 Carpet, heavy on concrete .20 - .30 Carpet, heavy on foam rubber .30 - .55 Concrete (smooth), painted .00 - .05 Concrete (smooth), unpainted .00 - .20 Concrete (block), painted .05 Concrete (block), unpainted .05 - .35 Cork, floor tiles (3/4" thick) .10 - .15 Cork, wall tiles (1" thick) .30 - .70 Drapery, light weight (10oz.) .05 - .15 Drapery, medium weight (14oz.), velour draped to half .55 Drapery, heavy weight (18oz.), velour draped to half .60 Fabric on Gypsum .05 Fiberglass, 3-1/2" batt .90 - .95

Fiberglass, 1" Semi-rigid .50 - .75 Glass .05 - .10 Gypsum .05 Linoleum on Concrete .00 - .05 Marble .00 Plaster .05 Plywood .10 - .15 Polyurethane Foam (1" thick, open cell, reticulated) .30 Rubber on Concrete .05 Seating (occupied) .80 - .85 Seating (unoccupied), metal .30 Seating (unoccupied), wood .30 Seating (unoccupied), fabric upholstered .60 Seating (unoccupied), leather upholstered .50 "Soundboard" (1/2" thick) .20 Sprayed Cellulose Fibers (1" thick on concrete) .50 - .75 Steel .00 - .10 Terrazzo .00 Wood .05 - .15


3/3

http://www.nrcratings.com/nrc.html

http://www.acoustical.com/documentation/acoustical-education/32-what-is-nrc-stc-and-saa-acoustical-material-distributors-inc

http://www.acoustical.com/documentation/acoustical-education/32-what-is-nrc-stc-and-saa-acoustical-material-distributors-inc
http://www.acoustical.com/documentation/acoustical-education/32-what-is-nrc-stc-and-saa-acoustical-material-distributors-inchttp://www.acoustical.com/documentation/acoustical-education/32-what-is-nrc-stc-and-saa-acoustical-material-distributors-inchttp://www.acoustical.com/documentation/acoustical-education/32-what-is-nrc-stc-and-saa-acoustical-material-distributors-inchttp://www.acoustical.com/documentation/acoustical-education/32-what-is-nrc-stc-and-saa-acoustical-material-distributors-inchttp://www.acoustical.com/documentation/acoustical-education/32-what-is-nrc-stc-and-saa-acoustical-material-distributors-inc

noise reduction coefficient

Documents