Comparison of wind turbine-only noise levels measured at operating wind farms in the United States to noise levels predicted using ISO 9613-2:1996

Abstract

This paper describes robust and effective methods for the measurement of noise emissions from utility-scale wind farms and the analysis of the resulting data for determining compliance with noise level limits and standards. The methods call for primarily unattended monitoring of noise levels, wind speeds, and turbine operating conditions over many weeks, in some cases months, in order to capture the recurring maximum wind turbine-only noise level at a receptor (i.e., residence). This condition occurs when the nearest turbines are producing full acoustic output while noise from background sources is very low (particularly that from wind). Presented are the results of noise compliance measurement studies applying these methods conducted by Hankard Environmental, encompassing eight projects and 35 measurement locations in the Northeast, Midwest, and Plains regions of the United States (U.S.) The results of these measurements are used to assess the accuracy of the ISO 9613-2:1996 method in predicting wind turbine noise levels at residences. These results can be used by wind energy developers to accurately design projects to meet applicable limits and standards and give all parties involved in the permitting process a greater degree of confidence in predictions and greater clarity during compliance measurements.