Note: Values shown are the NC curve octave-band pressure limits. Room NC tables may show adjusted values reflecting project-specific acoustic targets. The NC number (e.g. NC-25) is the authoritative performance criterion — the octave-band table is the implementation detail.
NC Curves — Standard Reference
Standard NC Curve Values (dB SPL)
| Frequency | NC-12 | NC-18 | NC-25 |
|---|---|---|---|
| 63 | 51 | 54 | 60 |
| 125 | 40 | 44 | 52 |
| 250 | 33 | 37 | 45 |
| 500 | 26 | 31 | 40 |
| 1k | 22 | 27 | 36 |
| 2k | 19 | 24 | 34 |
| 4k | 17 | 22 | 33 |
| 8k | 16 | 21 | 32 |
Per-Room NC Budget
| Room | NC Target | HVAC Max Contribution | Transmitted Max | Margin |
|---|---|---|---|---|
| VO Live B304 | NC-12 | NC-10 (IDU-04 min fan) | NC-10 | 5 dB |
| Control Room B311 | NC-18 | NC-15 (IDU-03 shared) | NC-15 | 5 dB |
| Video Studio B312-1 | NC-18 | NC-15 (IDU-05) | NC-15 | 5 dB |
| Editing Suite B312-2 | NC-25 | NC-22 (IDU-03 shared) | NC-25 | 5 dB |
Silencer Comparison
| Run | Serves | Length | Attenuation | NC Max After |
|---|---|---|---|---|
| Run A | VO Live (IDU-04) | 1,500mm | 40 dB | NC-12 |
| Run B (trunk) | Control + Editing (IDU-03) | 1,000mm | 25 dB | NC-18 |
| Run B1 (branch) | Control Room | 500mm | 15 dB | NC-18 |
| Run B2 (branch) | Editing Suite | 300mm | 10 dB | NC-25 |
| Run C | Video Studio (IDU-05) | 1,000mm | 25 dB | NC-18 |
Tangent Method Explanation
NC rating = highest NC curve touched by the measured spectrum.
Measure the sound pressure level at each octave band. Plot the values on the NC curve chart. The NC rating is determined by the highest NC curve that any measured value touches or exceeds. A single octave band exceeding the target curve defines the room's NC rating.