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What is NRC?
NRC stands for noise reduction coefficient and is the standard rating for how well a material absorbs sound. Different materials have different NRC ratings that range from 0.00-1.00.
Noise Reduction Coefficient Explained
Typically, the NRC rating of a material is viewed as a percentage. For example, an NRC rating of .75 means 75% of the sound energy coming in contact with that specific material is absorbed. Simply put, the sound is not reflected back into the room to create noise. A material with an NRC of 0.75 would also be considered 25% reflective.
- Although NRC is often thought of as a figure used for rating acoustic products, in reality, every material around us has an impact on acoustics and can be tested for a rating.
- The NRC figure ranges from 0.00—perfectly reflective—to 1.00—perfectly absorptive. NRC is always expressed as a decimal that is rounded to the nearest 0.05. For example, an unpainted brick that absorbs very little sound may have a rating of .05 while 1-inch-thick cork wall tiles may be extremely absorptive, with a rating of .70.
- So, what does this mean to you? A loud, reverberant room will need additional sound absorption. Materials with a rating of .75 or higher are generally considered to be highly absorptive and will bring about the best results; this includes cork, fiberglass, stone wool and sprayed cellulose fibers.
Everyday carpeting and drapes are often thought to be good for sound absorption, but, surprisingly enough, most have a rating of .35 or less! Typically, these materials absorb high frequencies, leaving middle and low frequencies unaffected.
What is a Good Noise Reduction Coefficient?
A good noise reduction coefficient is typically anything above 0.45, but it also depends on how much sound absorption a space requires. In a small space such as a conference room, you can get away with more aesthetic acoustic panels with lower NRC ratings, because echo tends to not be as bad in smaller rooms. However, in a large auditorium or church, you’ll need 2″ thick acoustic wall panels with an NRC of 1.
When it comes to echo in your house, you likely don’t need to install any acoustic panels. Anything with a mid-range NRC, such as area rugs, drapes, plush couches and other furniture and decor is going to cut down any echo you would otherwise experience.
Common Materials With Ratings
NRC Rating Chart
So we can see from this table that marble has an NRC rating of 0 and it is completely reflective. This is going to mean that it absorbs 0% of sound. The acoustic panels from our sister company Commercial Acoustics have an NRC rating of 1 and are completely absorptive. This means that they will not reflect any sound waves back in a room to create noise.
When NRC Products Are Useful
These sound absorbing panels are great to use in large spaces such as restaurants, worship centers and auditoriums. Large spaces fill with hard surfaces, like the ones listed, tend to have poor acoustics and that can be an issue with spaces where people need to listen to others speak.
For example, restaurants will install acoustic panels to increase the speech intelligibility in the space. For those who frequent restaurants or work in one, you’ll notice that most of them won’t have carpets and this is because it’s so much harder to clean than say a tile floor. If they didn’t use sound absorbing panels, people wouldn’t be able to understand each other due to all of the echo and reverberation coming off the hard walls and floors.
If You Want To Block Noise
While the acoustic panels work to absorb sound to reduce echo and reverberation, our soundproof curtains work in a different way. They are lined with mass loaded vinyl, which blocks sound rather than absorbing it. Products that block sound are given an STC rating, which tells you how many decibels it blocks. We go more in depth about this in our STC Rating blog if you’re interested in learning more about the abilities of our soundproof curtains.
At Residential Acoustics, we pride ourselves on helping you reduce the sound in your bedroom, living room and office with quality, state-of-the-art products such as the AcousticCurtain™ and AcoustiDoor™! These soundproofing products can stop 60%-90% of outside noise from entering a room.
In Conclusion- Noise Reduction Coefficient
The NRC or noise reduction coefficient of a product will tell you how much sound a product absorbs as well as how much it reflects. If a material has an NRC rating of 0.35 it absorbs 35% of sound and will reflect the remaining 65% of sound waves back into a room. Hard material, such as marble or tile have poor sound absorbing abilities while softer materials such as carpet will have better sound absorbing abilities.