Methods for assessing background sound levels during post-construction compliance monitoring within a community

摘要

One of the most challenging aspects to wind turbine noise compliance measurements is the subtraction of background sound to calculate a turbine-only sound level. In the United States, a variety of methods have been used, including concurrent measurements at proxy background, using a monitor that is shielded from wind turbine noise with barriers or buildings, and shutting down the turbines. In our experience, as related in this paper, the most accurate method is shutting down turbines near to the monitoring location, so long as background wind and sound conditions are similar between the turbine-on and turbine-off periods. The shielding method can be accurate under circumstances where the building or barrier is large enough to block a substantial portion of sound, only the A-weighted level is of interest, and there are few localized sources of background sound. The shielding method increases in accuracy with increasing wind turbine sound. The proxy location method is the least accurate, especially for standards based on the equivalent average, as it is very difficult to find two locations spaced several kilometers away that have concurrently similar background sound levels.