### Strutt Help

NRC Rating
**Strutt|Criteria|Ratings|Absorption|NRC** calculates the Noise Reduction Coefficient (NRC) of the current row of the worksheet

In an octave band sheet, NRC is calculated as:

`NRC=(alpha_(250)+alpha_(500)+alpha_(1k)+alpha_(2k))/4`, rounded to the nearest 0.05

In a 1/3 octave band sheet, NRC is calculated as:

`NRC=(alpha_(200)+alpha_(250)+alpha_(315)+alpha_(400)+alpha_(500)+alpha_(630)+alpha_(800)+alpha_(1k)+alpha_(1.25k)+alpha_(1.6k)+alpha_(2k)+alpha_(2.5k))/12`, rounded to the nearest 0.05

where:

`alpha_(x)` is the absorption coefficient in each octave or 1/3 octave band.

Comments or suggestions to
strutt@arup.com