NRC (Noise Reduction Coefficient) is a single number between 0 and 1 that measures how much sound a material absorbs. An NRC of 0 means total reflection — all sound bounces back. An NRC of 1.0 means complete absorption. For commercial acoustic treatment in Australian offices, classrooms, and aged care facilities, panels with an NRC of 0.80 or above are typically required. SoundFix Acoustics melamine acoustic panels achieve NRC ratings of 0.80–0.90+ depending on panel thickness, as independently verified by CSIRO.
If you’ve been specifying acoustic panels, reviewing product data sheets, or briefing an acoustic engineer, you’ve encountered the term NRC. It’s the single most cited performance metric in commercial acoustic treatment — and also one of the most misunderstood.
This guide explains what NRC means, how it’s measured, what rating different spaces require, and how to use it to specify correctly — for architects, facility managers, and project managers alike.
NRC stands for Noise Reduction Coefficient. It is defined in ASTM C423 and measures sound absorption across the mid-frequency range: 250 Hz, 500 Hz, 1,000 Hz, and 2,000 Hz. The NRC value is the arithmetic average of the absorption coefficients at those four frequencies, rounded to the nearest 0.05.
NRC is measured in a certified reverberation room by a NATA-accredited laboratory — in Australia, typically CSIRO. A standardised panel sample is installed in the chamber; reverberation time (RT60) is recorded before and after at each frequency band. The reduction in decay time determines the absorption coefficient at each frequency.
CSIRO Independent VerificationSoundFix Acoustics panels have been independently tested by CSIRO (Report No. AC222-02-1) under AS ISO 354–2006 and AS ISO 11654–2002. Test specimen: 40 mm Bevel Edge melamine panel, 700 × 700 mm, NATA-calibrated instrumentation, 18°C. View our verified project results →
The table below shows sound absorption coefficients across the full frequency spectrum and the resulting NRC rating at three panel thicknesses. Source: CSIRO Report AC222-02-1 (AS ISO 354–2006 / ASTM C423).
| Thickness | 125 Hz | 250 Hz | 500 Hz | 1,000 Hz | 2,000 Hz | 4,000 Hz | NRC |
|---|---|---|---|---|---|---|---|
| 25 mm | 0.05 | 0.22 | 0.54 | 0.74 | 0.88 | 0.92 | 0.60 |
| 40 mm | 0.10 | 0.39 | 0.85 | 1.00 | 1.00 | 1.00 | 0.80 |
| 50 mm | 0.15 | 0.46 | 0.95 | 1.00 | 1.00 | 1.00 | 0.90 |
At 500 Hz — the range most critical for speech intelligibility — the 40 mm panel achieves 0.85 vs 0.54 for the 25 mm panel. For education and aged care spaces where speech clarity is non-negotiable, 40 mm or 50 mm panels are strongly recommended.
NRC is a property of the material — how absorptive a panel is. RT60 (Reverberation Time) is a property of the room — how long sound takes to decay by 60 dB after the source stops. NRC is the input; RT60 is the output. High-NRC panels reduce a room’s RT60. For most Australian commercial spaces, a target RT60 of 0.4–0.8 seconds is appropriate.
Acoustic engineers set a target RT60 for a space based on its function, then calculate what NRC-rated surface area is required to achieve it. SoundFix Acoustics delivers the panels and documents the before-and-after outcome on every project.
| Space Type | Recommended NRC | Outcome |
|---|---|---|
| Classroom / Learning Space | 0.70 – 0.85+ | Supports speech clarity; meets BB93 & AS/NZS guidelines |
| School Hall / Gymnasium | 0.70 – 0.80+ | Reduces RT60 from 6+ seconds to under 2.2 seconds |
| Open Plan Office | 0.80 – 0.90+ | Reduces cocktail party effect; improves focus & productivity |
| Boardroom / Meeting Room | 0.85 – 0.95+ | Eliminates echo; improves speech intelligibility for conferencing |
| Aged Care — Dining & Common | 0.80 – 0.90+ | Reduces noise-related agitation; improves resident wellbeing |
| Restaurant / Hospitality | 0.75 – 0.90+ | Reduces dB levels; improves dining experience & dwell time |
NRC alone does not determine the acoustic outcome of a room.Coverage area, room geometry, and existing surface materials all influence RT60. A correct specification requires a site assessment. SoundFix Acoustics provides complimentary assessments for qualifying projects. Book your free assessment →
Acoustic performance in Australian schools is governed by the Building Code of Australia, with international frameworks widely referenced — including the UK’s Building Bulletin 93 (BB93) and the American ANSI S12.60 classroom acoustics standard.
BB93 sets a target RT60 of 0.4–0.6 seconds for classrooms and 0.8–1.2 seconds for larger halls. Achieving these targets in hard-surfaced Australian school builds generally requires NRC 0.70 or above, installed across 20–40% of ceiling surface area.
Students on the autism spectrum or with auditory processing disorders are disproportionately impacted by poor acoustics. Research links high-reverberation environments with reduced speech perception, increased cognitive load, and elevated stress. An NRC 0.80–0.90 specification supports every student — and particularly those who need it most.
See our Education Acoustics page for sector-specific guidance.
Open-plan office acoustics present a specific challenge: not just reverberation, but speech privacy and distraction. Ceiling panels with NRC 0.80–0.90 installed across the ceiling plane significantly reduce the ‘cocktail party effect’. Studies consistently link acoustic comfort with productivity gains of 5–10% in knowledge worker environments.
For boardrooms, the target is speech intelligibility for in-room and conferencing participants. RT60 targets of 0.3–0.5 seconds are appropriate, requiring panels with NRC 0.85–0.95+. See the Enbarr Melbourne commercial case study →
High reverberation in aged care dining rooms, common areas, and corridors contributes to agitation in residents with dementia, reduces speech intelligibility for those with hearing loss, and increases stress for staff and visitors.
The evidence base from dementia care research strongly supports NRC 0.80–0.90 specification across dining rooms and common areas. Panels in soft, warm tones can be integrated without disrupting the residential aesthetic that aged care design demands.
SoundFix Acoustics provides complimentary acoustic assessments, CSIRO-tested panels, and professional installation across Australia — with before-and-after RT60 documentation on every project.
Architecture firms: the sample box includes the full colour range, data sheet, and fire test certificate.
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