Paragraph 4 I1

If the measured noise level from the authorised development (including the application of any tonal penalty as per paragraph 3) is above the limit set out in the requirements, measurements of the influence of background noise shall be made to determine whether or not there is a breach of Requirement 30 or 35. This may be achieved by repeating the steps in paragraphs 1 and 2 with all of the wind turbines switched off in order to determine the background noise, L3, at the assessed wind speed. The wind turbine noise at this wind speed, L1, is then calculated as follows, where L2 is the measured noise level from the authorised development at the assessed wind speed with turbines running but without the addition of any tonal penalty—

The measured noise level from the authorised development is re-calculated by adding the tonal penalty (if any) to the corrected noise level L₁.