We receive a lot emails asking to explain the abbreviation "NRC". So we thought we'd add an article to help explain it.
'NRC '(Noise Reduction Coefficient) is a number that rates the capability of a material to absorb sound. Why would you want to absorb energy?
A room which has a lot of reflective surfaces will allow sound to build up and build up, getting louder and louder. Reflective surfaces that cause problems include hard floors, bare ceilings and walls. Glass partitions and long desks also increase echo which is also called reverberation.
Not all reverberation is bad. For example, a choir singing hymns within a church makes us of this natural reverberation. This echo adds to the harmonics of the end sound. In comparison, you would not want the same reverberation time in a lecture hall or large office space. It can disrupt conversations between colleagues, harming productivity and learning. This is why we need to place materials around the classroom or office to help absorb some of this energy.
We work out the NRC by taking the average of how absorbent a material is at four specific frequencies. These 4 frequencies are 250hz, 500hz, 1000hz, and 2000hz. (The lower frequencies are harder to absorb because the wavelengths are so long). The 250 to 2000hz is an average of mid-range speech frequency. This implicates that using the NRC value for a product to absorb music is pointless. This is because music utlises the full frequency range. Instead it is very effective for working out the effectiveness for offices, restaurants or classrooms.
After each material is tested, it is assigned an NRC rating. This can range from 0 to 1.00. Ratings are rounded to the nearest .05. These values can exceed 1.00 when thick materials or materials with large air spaces are being tested. Also, a test material’s area does not include the sides of the panel, which are exposed to the test chamber. Depending on the thickness of this, NRC results can vary.
Because the NRC is an average, two materials with the exact same NRC can perform differently. One might give better absorption at lower frequencies while the others works better at higher frequencies. Each may absorb better at different frequency levels, and work differently in different environments.
SAA (Sound Absorption Average) is a newer, more precise test method of an NRC. Whereas NRC ratings are rounded to the nearest .05, SAA is rounded to the nearest .001. We display the full acoustic data, including absorption for individual frequencies. this makes it easier for you see
NRC should not be confused with STC (Sound Transmission Class). The key difference between NRC and STC is that NRC is used to rate materials that ABSORB sound. STC is used to rate materials that BLOCK sound.
So if you have had a test report completed and within that report it includes guidance on what the acoustic performance of a product should be and the coverage required for that given space we can use that information to guide you to a range of products that will be suitable for that application.