Strutt|Criteria|Curves|Sound Levels|NC inserts the Noise Criterion (NC) curve into the active row of the worksheet. The user may select which NC curve to display by entering the curve number in Column D of the active row.
Please note that the NC curve is only from NC15 in 5 unit intervals to NC70. If an intermediate value is entered, Strutt returns the nearest NC curve - thus entering NC26 will return the NC25 curve, for example.
Reference: Table 18.3, Noise and Vibration Control (Beranek)