**6. Summarizing our proposal for predicting sound pressure levels related to the operation of large wind turbines**

Our proposed calculation process has two steps: at first, modeling the noise generation and its propagation in the short scale (less than 100 m); and propagating the output of the first step from short to large distances far away from the source. At the beginning of the process, the atmospheric stability class is to be taken into account by a correction to the wind velocity; this is very important, to avoid underestimations.

#### **Figure 5.**

*Comparison of results; left bar: Measured sound pressure levels; center bar: ISO 9613-2 predicted sound pressure levels; left bar: Our prediction proposal. All sound pressure levels are in dBZ. (Adapted from [10]).*


*Prediction of Environmental Sound Pressure Levels from Wind Farms: A Simple but Accurate… DOI: http://dx.doi.org/10.5772/intechopen.103159*


**Table 7.**

*Comparison between our attenuation curves and those from [18].*

**Figure 6.** *Calculation process of this prediction proposal (adapted from [10]).*

The first step of the calculation process divides the blade in infinitesimal length slices that behave as point sources, and for them the sound pressure level associated to the three mentioned generation processes for each source is calculated and summed logarithmically.

The propagation model takes into account the geometric divergence and the atmospheric absorption, considering *n* as *n*(fi, d u). Our proposed "n" values have been presented in Section 3. The fact of not working under the usual hypothesis of environmental acoustics allows considering the coefficient "*n*" as variable.

**Figure 6** shows a sketch of the procedure.
