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Resonics Guide to Sound Absorption Classes
If you've been looking into acoustic panels, chances are you've come across the term sound absorption classes. But what exactly does it mean, and why does it matter?
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TL;DR – Understanding sound absorption classes
Sound absorption measures how well a material absorbs sound instead of reflecting it. Hard surfaces cause echo and reverberation, making spaces noisy and uncomfortable.
Acoustic panels reduce this by using porous materials that trap and absorb sound energy (converting it into small amounts of heat or vibration), improving clarity and lowering background noise.
Panels are rated by sound absorption class (A–E) or NRC (0–1):
The right choice depends on the room’s size, surfaces, furnishings, and how it’s used. Too little absorption won’t help, but too much can make a space feel unnaturally quiet.
What is Sound Absorption?
Sound absorption is a way of measuring how well a material can absorb sound energy.
When sound waves hit a hard surface, like concrete, glass or plaster, they bounce back into the room, creating unwanted echo and reverberation. This is what makes spaces feel noisy, chaotic or uncomfortable.
How do acoustic panels absorb sound?
Acoustic panels are made with porous materials that allow sound waves to travel through the surface and be absorbed.
When sound hits an absorbent surface, a portion is reflected, some passes through, and the rest is absorbed (usually converted into a small amount of heat or vibration). The more sound a material can absorb, the more it helps to reduce background noise, improve clarity and create a better acoustic environment.
Not all acoustic panels perform the same. Their effectiveness depends on:
- Thickness
- Core material
- Surface finish
As a general rule, the thicker and more porous the panel, the more sound it absorbs.
Understanding sound absorption classes
To make comparison easier, acoustic panels are grouped into absorption classes, from Class A (highest performance) to Class E (lowest performance). They are tested across a range of frequencies and assigned an absorption coefficient, which indicates how much sound it absorbs.
Class A panels are highly effective at reducing reverberation and are the go-to choice for spaces with significant noise issues. Class E panels offer minimal absorption and are typically used in spaces with lower acoustic demands.
Panels may also be given a NRC (Noise Reduction Coefficient) rating instead of a class. This number ranges from 0 to 1:
- 0 = absorbs no sound
- 1 = absorbs nearly all sound
For example, a NRC of 0.95 is equivalent to Class A.
Guide to choosing acoustic panels based on absorption class
Which absorption class is right for you?
Not every space needs the same level of absorption. A lively school hall will need a very different approach than a small meeting room or open-plan office. Factors that influence your requirements include:
- Ceiling heights
- Surface finishes
- Room size
- Furnishings
- How the space is used
Too little absorption won’t make much difference. But too much can leave a space feeling dull or unnaturally quiet.
Class A (NRC 0.90 – 1.0)
Excellent absorption. If a room feels loud, echoey or overwhelming, Class A is usually the answer.
Best for: Open-plan offices, sports halls, industrial spaces, village halls, restaurants, churches, studios or any space with high reverberation.
Acoustic wall panels with Class A absorption:
Acoustic ceiling panels with Class A absorption:
Class B-C (NRC 0.60 – 0.85)
Good to very good absorption. It’s ideal for moderate noise control where clarity matters but extreme treatment isn’t required.
Best for: Offices, meeting rooms, classrooms, residential spaces, corridors and circulation areas.
Acoustic wall panels with Class B absorption:
Acoustic ceiling panels with Class B absorption:
Class D-E (NRC 0.15 – 0.55)
Limited absorption. Usually selected for visual design rather than performance but when paired with other acoustic treatments can be effective.
Best for: Acoustic screens and room dividers.
Products with Class D and Class E absorption:
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Need guidance? We’re here to help.
Choosing the right acoustic solution shouldn’t feel complicated.
That’s why we offer free, no-obligation acoustic surveys, either in person or remotely. We’ll:
- Assess your space
- Calculate what’s required
- Recommend the right absorption class
- Provide a clear, tailored treatment plan
Whether you’re looking to reduce echo, improve speech clarity or create a more comfortable environment, we’ll help you strike the perfect acoustic balance.
