The potential noise impact of a wind farm is assessed during the design phase, and is achieved through the following steps:

Step 1: Noise measurement.
Measurements of the existing background noise levels are undertaken at noise sensitive residences in accordance with recognized standards and guidelines. This allows an analysis to be completed to determine the existing baseline background noise level.

Step 2: Noise limits.
A suitable limit is placed on the wind farm based on the existing background level and appropriate noise Standards and guidelines. These limits are set by relevant authorities such as the Environment Protection Authority (EPA).

Step 3: Noise level predictions.
Using the proposed wind farm layout, predictions of the noise levels at the noise sensitive residences are completed to ensure that the layout complies with the noise limits set by the EPA.

At the time of predicting the noise levels at nearby houses, noise level predictions are generally completed for an extensive area around the proposed wind farm site. These predictions are usually represented as "iso-noise" maps, where the "contours" shown are the predicted noise levels. An example is shown in the following figure. These predictions can be undertaken for different operational wind speeds.