This chart shows the frequency spectrum of the noise emissions at the exit of the L-1 Vertical Wind Tunnel located at Appalachian Amusement Center with the fan blades removed for inspection. Comparing this to the same test with the fan blades will help to isolate which part of the emission is generated by mechanical noise, and which is generated by air moving though the machine. This will help to determine what improvements can be made. The meter was located two feet above and two feet away on the building side from the exit (where the wind comes out of the machine) with the transducer pointing toward the center of the exit. At the time these measurements were made, there was some intermittent wind and background noises such as passing vehicles and someone using a chain saw in the distance. While great care was taken to make the measurement between occurrences, some of these measurements may be slightly higher. This may explain why the ambient reading is higher then when the HVAC was running. These measurements show that the HVAC and drive cooling fan noise is barely perceptible at the exit during quiet conditions. It also shows the primary frequencies of the sound generated by the fan and drive are between about 250 and 1000 Hz, among other things.

Image shows sound meter located 2 feet out and two feet above the exit.