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What Is Noise Reduction Coefficient (NRC) Rating? — Acoustic and Sound Rating of Materials

NRC Rating

Noise Reduction Coefficient Rating (NRC) rating is basically how well a particular product or material absorbs sound.

The decimal values you see in soundproof products on the market? That’s NRC.

But here’s the thing: it’s way too usual to win over with many technical terms and processes. With words like frequency, decibels, linearity – you can get lost in a snap!

That’s why we’ve come up with the briefest and quickest way to explain NRC so you understand it without scratching your head. Let’s begin!

Table of Contents

What Is an NRC Sound/Acoustic Rating?

Noise Reduction Coefficient – commonly abbreviated as NRC is an average rating of how much sound an acoustic or sound product can absorb at specific mid-range frequencies (tested with four intervals of 250 Hz, 500 Hz, 1000 Hz, and 2,000 Hz).

Seems too much? Let’s chop it down.

Think of It Like This…

If you strike a wall with a hammer, for example, there is a corresponding rate because you produced a sound.

The sound energy absorbed by the wall will have a respective coefficient rating.

Each coefficient value undergoes a thorough calculation in specific mid-range frequencies of four octaves. This is to cover the frequency values of a typical person’s speech.

Too technical?

Simply put, an NRC rating is a represented value that defines how well a particular product or material will absorb sound in human speech frequencies.

This value ranges from 0 to 1 where;

  • 0 – does not absorb sound well
  • 0.75 to 1 – absorbs sound well

Coefficient Interpretation

The higher the NRC rating, the better the product or material is at absorbing sounds. 

If the test measurement is zero, it indicates a “perfect reflection” where a product absorbs no sound waves. If it’s one, it is a “perfect absorption” where a product absorbs all sound waves.

Generally, a percentage interprets each value. So the next time you read that a material has a .80 rate, it only means that 80% of the sound is designed for sound absorption, while the other 20% is for sound reflection.

The NRC Ratings of Different Materials

There are tons of sound-absorbing materials you can get your hands on. Heck, even soundproof acoustic paint is a thing!

But NRC ratings vary per material due to many factors such as its medium absorbent, thickness, density, and edging effect, and a whole lot more. (You’ll get to know more about these as you go on this article!) 

We’ll provide you the coefficient ratings of different materials for you to make an accurate decision when selecting a solution for your acoustic system and next project:

1. Marble

Marble is the most common example of a material that contains a low-rated noise reduction coefficient.

The main component of marble is calcium carbonate. This makes it the best substance to reflect sound due to its density and strength. It is known to have a 0.01 NRC rating.

It only means that it doesn’t do any sound absorption! The material’s reflective properties mean that it’s not pretty handy for a noisy home that requires the ability for acoustic control.

Ever wonder why home kitchens might be a bit noisier than your other rooms of the house? Marble-made kitchen fixtures negatively affect the need for acoustic absorption.

2. Drywall

Drywall is a type of board made from plaster, wood pulp, or other particulars used in building your home.

With its natural ingredient of calcium sulfate dihydrate, this type of wall provides a 0.15 NRC rating.

There are different types available in the market where each category may contain distinct degrees of thickness. These variations highly contribute to precise coefficient scores.

Try this on your next project! Even better, construct a double layer of drywall for a higher NRC!

3. Carpet

Placing a carpet in any place would interestingly contribute to the NRC rate. It averages at around a 0.4 NRC rating.

However, a thin carpet would have a lower NRC resulting in reflecting more sound than absorbing it. The thicker the medium, the more acoustic absorption there is.

The cool thing about carpets is it’s known to be the best floor product for soundproofing acoustics. An example of a highly recommended technique for sound absorptions includes carpeting and drapes in rooms or areas.

It’s probably the reason why all recording studios have carpeted flooring.

4. Acoustic Ceiling Tiles

One of the highest on the list, acoustic ceiling tiles has a coefficient of 0.7 NRC rating.

A score of 0.7 is usually sufficient for individuals wanting to achieve a simple soundproof starter house feature.

This material controls the acoustic features in two ways: (1) absorbing acoustic waves that prevent the sound from bouncing around walls or (2) blocking acoustic waves from traveling.

This material is best for large spaces like restaurants and churches.

5. Acoustic Panels

Probably the highest possible NRC rate ever recorded are acoustic panels, (usually placed on walls) with a perfect 1.0 NRC rating.

That 1.0 rate means the effect of these panels is practically perfect as sound absorbers.

High-quality acoustic panels give you the soundproof experience to meet your needs, especially in a large area, space, or room where acoustics can be awful. Their goal is to reduce noise levels and decrease reverberation in the walls.

So if you’re eyeing to control the acoustics of your room to ease talking with each other, acoustic panels boost the sound quality at a much quicker rate.

You can even make your own DIY panels if you’re not willing to spend yet on more expensive high-quality ones!

What Is Considered as a Good NRC Rating?

If you’re on the lookout for a good rank value, NRC ratings of .75 or higher are generally considered highly absorptive.

So if you’re on the hunt for an “add to cart” solution to a noise problem in your room or space, make sure to consider all acoustic products and sound absorption materials with NRC ratings of 0.75 or higher.

What Is the Best NRC Rating?

The two most important conditions when considering their NRC values are thickness and density. If a medium is known to be efficient to absorb sound, it also follows that it’s thick and dense.

The winning question of all time now is What is the Best NRC Rating?

Well, here’s the deal: the results with a higher NRC rate = better conditions.

Go with hard, dense, and impenetrable products or materials like MLV (Mass Loaded Vinyl).

Additionally, nobody should tell you to limit your space in using one product or material. Spice up your spaces with as many absorbers as you want!

How Is the NRC Value Calculated?

Unfortunately, not everyone can accurately measure the rate of an acoustic product or medium without the help of trained professionals.

Here’s a quick process on how each value undergoes calculation of their performance:

  • Initial measurement is taken in a sound test laboratory room by noise signal transmission through a microphone.
  • Once done, the product or material undergoes the same testing at the same test laboratory room. Now with four different noise frequencies (250 Hz, 500 Hz, 1000 Hz, 2000 Hz).
  • The gathered test measurement calculations are an average. A decimal rounded off to the nearest 0.05 is reported for every NRC.

A sound absorption coefficients’ value indicates that the material provides an acoustic surface area equivalent to its physical, two-dimensional surface area.

Simply put, any material or product that is three-dimensional or greater exceeds the 1.00 NRC ratings’ limit.

NRC ratings over 1 are possible. If you read a value above 1.0 in acoustic products, this is due to edges inclusion in the equation, called the “edge effect.”

What’s the Difference Between NRC and STC Rating?

Whenever people decide to purchase any soundproofing products and provide testing, the NRC rating is usually compared with the STC rating.

NRC talks about the rating system on how much sound that a product can absorb. Picture it as a grading scale where you can assess products’ absorptive capacity.

Difference Between NRC and STC Rating

On the other hand, Sound Transmission Class (STC) is a class of material that reduces acoustics going through structures’ medium. It serves as the barrier against acoustic inputs “attacking” your space.  

In terms of rate classification, the two concepts you need to understand are that:

NRC measures the build-up of noise within a space or room while STC measures the sound transmission between space or room.

Both are useful performance factors to further improve the soundproofing quality in your room.

Conclusion

NRC is the standard rating for how well a material absorbs sound waves and how much it reflects at specific mid-range frequencies.

The basis of measurements is if the noise reduction coefficient includes zero (perfect reflection) to one (perfect absorption). It undergoes a meticulous process of performance testing, but here are a few pointers to remember:

  • Products or materials that are hard, dense, and have impenetrable compositions – such as marbles or tiles – have poor sound absorption.
  • Products or materials that are soft, thin, and have penetrable compositions – such as carpets or acoustic panels – have better sound absorption.

FINAL TIP: To fully understand what soundproofing entails, you can read up on The 5 Soundproofing Principles to help you out.

About the Author

andrea_adams

Andrea has always been bombarded by the hustle and bustle outside her home. Living in the city doesn’t get any quieter. The never ending noise from construction, traffic, and dogs barking on the streets day in and day out drove Andrea to a breaking point.

For 3 years, Andrea committed herself to studying DIY hacks, performing soundproofing experiments, and installing noise-free solutions. Now, she lives a quiet life free of the stress from noisy environments.

She hopes to share this knowledge so that others don’t have to endure the noise reigning in their ears and live a peaceful, stress-free life.