Audio
NC Rating
Also called: Noise Criteria, NC curve
A single-number rating of a room's background noise level across frequency bands, used to judge whether mechanical noise will interfere with speech and conferencing.
Conference rooms should generally land around NC 30–35; open offices tolerate more. The number matters because every dB of HVAC rumble eats into microphone gain before feedback, and because echo cancellation performs worse with a high noise floor. A room measured at NC 45 will disappoint on video calls regardless of the AV budget.
NC is worth measuring before design, not after complaints. If a room reads high, the fix belongs to the mechanical contractor — duct lining, diffuser changes, fan speed — and it is far cheaper to raise before ceilings close than to chase with signal processing afterwards.
Related terms
- RT60
- The time in seconds for sound in a room to decay by 60 dB — the standard measure of how reverberant a space is and how intelligible speech will be in it.
- AEC
- Processing that subtracts the room's own loudspeaker output from the microphone signal so remote participants do not hear their own voices echoed back.
- Sound Masking
- A system that emits precisely shaped background sound across a ceiling to raise the ambient noise floor, making nearby speech unintelligible and improving acoustic privacy.
More Audio terms
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