Environmental Engineering Reference
In-Depth Information
CHAPTER 20
and abatement methods
Panagiota Pantazopoulou
BRE, Watford, UK.
This chapter presents an overview of the types, the measurements and the potential
acoustic solutions for the noise emitted from wind turbines. It describes the fre-
quency and the acoustic signature of the sound waves generated by the rotating
blades and explains how they propagate in the atmosphere. In addition, the avail-
able noise measurement techniques are being presented with special focus on the
technical challenges that may occur in the measurement process. Finally, a discus-
sion on the noise treatment methods from wind turbines referring to a range of the
existing abatement methods is being presented.
1 Introduction
Wind turbines generate two types of noise: aerodynamic and mechanical. A tur-
bine's sound power is the combined power of both. Aerodynamic noise is gener-
ated by the blades passing through the air. The power of aerodynamic noise is
related to the ratio of the blade tip speed to wind speed. The mechanical noise is
associated with the relevant motion between the various parts inside the nacelle.
The compartments move or rotate in order to convert kinetic energy to electricity
with the expense of generating sound waves and vibration which is transmitted
through the structural parts of the turbine.
Depending on the turbine model and the wind speed, the aerodynamic noise
may seem like buzzing, whooshing, pulsing, and even sizzling. Downwind tur-
bines with their blades downwind of the tower cause impulsive noise which can
travel far and become very annoying for people. The low frequency noise gener-
ated from a wind turbine is primarily the result of the interaction of the aerody-
namic lift on the blades and the atmospheric turbulence in the wind. High frequency
noise is also generated due to the interaction of the air turbulence and the blades
during their rotation, constantly changing angle of attack.
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