Measurement and analysis of wind-induced background noise levels for wind turbine generator impact assessment

摘要

For many of the local jurisdictions in the State of California, the criteria for assessing the noise impact from wind turbine generators allow adjustment for existing ambient noise levels. Since the noise generated by wind turbine generators is a function of wind speed, characterizing the ambient noise must also be done as a function of wind speed. This has been done for a number of wind farm projects with different topography and receiver configurations. By cross plotting sound level with wind speed, the speed at which the ambient is dominated by wind-induced noise due to flow interaction with structures and vegetation can be determined and modeled using a dipole source model that relates sound level to wind speed to the sixth power. In performing this analysis, larger percentile metrics such as the level exceeded 50 or 90% of the time are found to be more suitable than time averaged, equivalent levels or smaller percentile metrics. With the larger percentile levels, it is also noted that microphone windscreen performance is not as critical in the background noise measurements. Several examples of the application of these windinduced background noise measurements to impact assessment for wind turbine generator projects are reviewed.