NRC Ratings: What Is a Noise Reduction Coefficient?

What is NRC?

In the simplest possible terms, a NRC (or Noise Reduction Coefficient) is the number which rates the effectiveness of a material at absorbing sound.

What Does A Noise Reduction Coefficient Mean?

NRC Ratings can range from 0 (indicating a perfectly reflective material) to 1 (indicating a perfectly absorptive material).

One way to look at NRC ratings is to see them as a percentage of sound that comes in contact with a sound absorption material and are not reflected back into the room.  For example, a Noise Reduction Coefficient of .7 would indicate that 70% of sound waves are absorbed by the material.

How is NRC Calculated?

The Noise Reduction Coefficient is calculated by averaging how absorptive a material is at four different frequencies: 250hz, 500hz, 1000hz, and 2000hz.

Because the “official” NRC is an average, two materials with the exact same NRC can perform differently in different applications.  Each may work best at a different frequency.

NRC vs. STC                                                                                                                           

NRC ratings are often confused with STC ratings, which are also commonly referenced in the acoustic treatment industry.  The key difference between NRC and STC is that NRC is used to rate materials that ABSORB sound, while STC is used to rate materials that BLOCK sound.

How Does Audimute Measure Up?

Audimute's Acoustic Panels have a Noise Reduction Coefficient of 1.0, perfectly absorptive.  The table below shows the NRC Rating of Audimute Acoustic Panels at various common frequency levels.  You can see that our acoustic panels are most absorptive at higher frequencies, like the frequency of high-pitched instruments or the human voice.  This is typical of any acoustic panel.

Audimute Acoustic Panels NRC Ratings