Wind Turbine Acoustics - Wind Turbine Technology: Fundamental Concepts of Wind Turbine Engineering - page 441

Figure 7-26. Calculated noise propagation downwind of a single row of wind turbines
in the example array for four atmospheric absorption rates. [Shepherd and Hubbard
1986]
Effect of Multiple Rows
Figure 7-27 presents the results of sound-pressure-level calculations that were made for
one, two, four, and eight rows of wind turbines; this illustrates the effects of progressively
doubling the number of machines for a constant turbine spacing. At zero atmospheric
absorption, and at receiver distances that are large relative to the array dimensions, a
doubling of the number of rows results in an increase of 3 dB in the sound pressure level.
This simply reflects a doubling of acoustic power. At shorter distances, the closest
machines dominate and the additional rows result in only small increments in the sound
Figure 7-27. Calculated noise propagation downwind of various numbers of rows of
wind turbines in the example array. [Shepherd and Hubbard 1986] (a) Without
atmospheric absorption. (b) Absorption coefficient a = 0.54 dB/100 m