Noise Criteria Curves: NC
NC-65#1000 to NC-70#125
Noise Criteria (NC) and Room Criteria (RC) curves for HVAC acoustics design. NC curves per ANSI S12.2-2008 from NC-15 through NC-70 (12 curves), and RC Mark II curves per ASHRAE from RC-25 through RC-50 (6 curves). Each curve has 8 octave band center frequencies (63-8000 Hz) with maximum allowable sound pressure levels in dB. Includes recommended occupancy type and equivalent dBA background noise level. 144 records total.
| criterion type | curve point | background noise dBA equivalent (dBA) | max sound pressure level dB (dB) | octave band center Hz (Hz) | rating | recommended occupancy |
|---|---|---|---|---|---|---|
| NC | NC-65#1000 | 75 | 66 | 1,000 | NC-65 | factory |
| NC | NC-65#125 | 75 | 75 | 125 | NC-65 | factory |
| NC | NC-65#2000 | 75 | 64 | 2,000 | NC-65 | factory |
| NC | NC-65#250 | 75 | 71 | 250 | NC-65 | factory |
| NC | NC-65#4000 | 75 | 63 | 4,000 | NC-65 | factory |
| NC | NC-65#500 | 75 | 68 | 500 | NC-65 | factory |
| NC | NC-65#63 | 75 | 80 | 63 | NC-65 | factory |
| NC | NC-65#8000 | 75 | 62 | 8,000 | NC-65 | factory |
| NC | NC-70#1000 | 80 | 71 | 1,000 | NC-70 | factory |
| NC | NC-70#125 | 80 | 79 | 125 | NC-70 | factory |
What else is in Engineering Database
AI built for engineering. Searches the engineering database, performs calculations, gives source-backed engineering insights.
Get started for free ↗Reference Data375 engineering tablesMaterial properties, pipe and shape dimensions, code tables, and electrical ratings across mechanical, civil, chemical, electrical, materials, and manufacturing engineering.
Browse dataCalculatorsDeterministic engineering calculatorsSizing, checking, and conversion tools that run against the reference tables. Inputs are code-compliant, outputs are traceable to the source standard.
Browse calculators