This chart shows the frequency spectrum of the noise emissions measured from the center of the bleachers at ear height of a sitting spectator, at the L-1 Vertical Wind Tunnel located at Appalachian Amusement Center. The meter was located in the center of the bleachers with the meter's transducer a measured diagonal distance of 66 feet, 2.5 inches from the center of the net, with the transducer pointing toward the center of the exit. There was no lower net during this test. The upper net contributed some noise. I chose 500, 550, 600 and 650 RPM because 500 RPM is the slowest that will fly a small adult, while 650 is the fastest we have turned the fan thus far

These images show the sound meter location in the bleachers