Strutt|Criteria|Curves|Sound Levels|NR inserts the Noise Rating (NR) curve into the active row of the worksheet. The user may enter the curve number into Column D of the active row to return a specific NR curve.
The NR curve is defined for integer curve numbers, and is calculated from the following formula:
`NR = A + B(NR#)`, where `NR#` is the curve number
and `A` and `B` are frequency-dependent coefficients defined as:
| Frequency | 31.5 Hz | 63 Hz | 125 Hz | 250 Hz | 500 Hz | 1 kHz | 2 kHz | 4 kHz | 8 kHz |
| A | 55.4 | 35.4 | 22.0 | 12.0 | 4.2 | 0.0 | -3.5 | -6.1 | -8.0 |
| B | 0.7 | 0.8 | 0.9 | 0.9 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 |
Note: Strutt rounds each curve value to 1 decimal place, using the `A` and `B` values above as defined in the standard
Reference: