Results have shown that the most probable source of this acoustic annoyance was the transient, 'unsteady aerodynamic lift imparted to the turbine blades as they passed through the lee wakes of the large, cylindrical tower supports.
Nearby residents were annoyed by the low-frequency, acoustic impulses propagated into the structures in which the complainants lived. The situation was aggravated further by a complex sound propagation process controlled by terrain and atmospheric focusing. Several techniques for reducing the abrupt, unsteady blade load transients were researched and are discussed.
This document summarizes the results of an extensive investigation into the physical factors surrounding noise complaints related to the DOE/NASA MOD-l wind turbine operating near Boone, North Carolina.
The authors wish to acknowledge the support and assistance of the following
organizations in SERI's MOD-l research:
• Appalachian State University
• The Blue Ridge Electric Membership Corporation
• Engineering Dynamics, Inc.
Cornell University, Sibley School of Mechanical and Aerospace
• The General Electric Company
• Massachusetts Institute of Technology, Department of Aeronautics and
• NASA Langley Research Center, Structural Acoustics Branch
• NASA Lewis Research Center, Wind Energy Program Office
• Pacific Northwest Laboratories, Atmospheric Physics Department
• Pennsylvania State University, Departments of Meteorology and Mechanical
• The Portland General Electric Company
• Rocky Flats Wind Energy Research Center
• University of Colorado-Boulder, Departments of Mechanical and Aerospace
• University of Virginia, Department of Environmental Sciences
Special thanks are extended to the residents of Boone, North Carolina,
particularly those near the MOD-l site who aided us in this investigation.
Some parts of the program could not have been accomplished without the help of
SERI staff members Stan Thues, Bob McConnell, and Jane Ullman. Benjamin Bell
was responsible for developing much of the computerized, time-domain analysis
technique. University of Colorado-Boulder (UCB) engineering undergraduates
Robert Wooten, David Dill, and Daniel Schell were responsible for supporting
the testing at the Rocky Flats Research Center and provided the bulk of the
support and planning for the testing in the UCB wind tunnel. This work was
supported by the DOE Wind Energy Technology Division under contracts
EG-77-C-Ol-4042 and DE-AC02-83CHl009