NRC and RT60 Explained: The Two Numbers That Matter in Acoustic Design
Ask three different suppliers about acoustic treatment and you'll hear two numbers over and over: NRC and RT60. They're not interchangeable, and mixing them up is the easiest way to end up with the wrong product for your space.
What is NRC?
NRC - Noise Reduction Coefficient - is a single number between 0 and 1 that rates how much sound a material absorbs, averaged across the frequency range most relevant to speech. A panel rated 0.85 NRC absorbs roughly 85% of the sound energy that hits it and reflects the rest. It's a product rating, tested in a lab, and it's what you'll see on an acoustic panel's datasheet.
What is RT60?
RT60 - reverberation time - measures something different: how long sound takes to decay by 60 decibels in an actual room once treatment is installed. It's expressed in seconds, and as a general guide, open-plan offices and meeting rooms are typically treated toward a shorter RT60 than a reception area, because speech clarity matters more where people are concentrating or holding a conversation. Exact targets vary by room use and size, which is why a proper survey matters more than a rule of thumb.
Why the difference matters
NRC tells you how good a product is. RT60 tells you what actually happened in your room. A high-NRC panel installed in too small a quantity, or in the wrong position, can still leave a room with a poor RT60. That's the gap between buying panels off a spec sheet and getting a space that actually sounds right, and it's why we survey and calibrate-test every project rather than just recommending a product.
See how this plays out at scale in our guide to treating large rooms and event halls.
Considering acoustic treatment for your space? Book a free site survey and we'll measure what's actually happening before recommending anything.
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