### Strutt Help

NR Curve

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:

• BS8233 (1999)