Strutt|Criteria|Curves|Sound Level|RNC inserts the Room Noise Criterion (RNC) curve into the current row of the worksheet.
The user may select which RNC curve to display by entering the curve number into Column D.
The RNC method is recommended to be used in cases where the services noise includes fluctuations or 'surging' at low-frequencies. Refer Section 5.3.2 of ANSI S12.2 for objective tests for surging/fluctuations
Reference: ANSI/ASA Standard S12.2 (2008) Criteria for Evaluating Room Noise