905461.fig.0012a
(a) PPS 12/2 turbulence grid
905461.fig.0012b
(b) PPS 14/4 turbulence grid
Figure 12: Leading edge noise third-octave band sound pressure levels, nominal flow speed = 35 m/s ( = 548,000), , (orange rectangle) 130,200, (faint blue circle) 8,200, (dark blue triangle) 1,000 Pa  , (grey —) empty test section, - - - Amiet model [5] according to (1), auto–spectrum of one single array microphone for a measurement at the nonporous reference airfoil.