Science is king in the world of acoustics. Having a visually pleasing product is great, but if it doesn't work well acoustically, there is no point. The acronym NRC stands for Noise Reduction Coefficient.
NRC is a single number value ranging from 0.0 to 1.0 that describes the average sound absorption performance of a material. An NRC of 0.0 indicates the object does not attenuate mid-frequency sounds, but rather reflects sound energy. Conversely, an NRC of 1.0 indicates that the material provides an acoustic surface area (in units sabin) that is equivalent to its physical, two-dimensional surface area.
The absorption coefficients of materials are commonly determined through use of standardized testing procedures, such as ASTM C423 that is used to evaluate the absorption of materials in eighteen one-third octave frequency bands with center frequencies ranging from 100 Hz to 5000 Hz.
The higher a NRC rating is to 1.0, the better it performs acoustically. The lower the NRC rating, the poorer it performs acoustically.
Most fiberglass acoustic panels have an NRC varying from 0.8 to 1.0, depending upon the thickness. Other popular acoustic products on the market generally have lower NRC ratings for example:
- PET felt board typically has a NRC rating around 0.4
- Pyramid and Egg Crate foam typically has a NRC rating varying from 0.3 to 0.6 depending upon the thickness
Sometimes NRC values will be listed using different mounting methods. These methods include furring out the acoustic product to create an air gap. This type of mounting can increase the overall performance of a product if installed correctly. The standard mounting method, (where the panel is mounted directly to the wall or ceiling) is called Type A Mounting.