This reproduction gives an overall impression of noise from a large airplane and its reduction using TMWE. It is not meant to be an exact replication of noise from an actual aircraft. To construct the sound presented here, the microphone time series recorded in our small-scale experiments (0.5-inch diameter jet nozzle) were "stretched" by factor of 80 to scale up to an exhaust diameter of 40 inches. Because the maximum frequency that can be resolved in our experiments is 200 kHz, the maximum frequency of the stretched data is 200/80=2.5 kHz. This means that the sound you hear in this reproduction has frequencies from 0-2.5 kHz, while humans can hear frequencies up to 20 kHz. If we could resolve higher frequencies (we need a bigger facility to do that), we believe that the reproduction would be similar to or better than this one because MWE does a great job of reducing high frequency components.
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Sound from untreated
engine exhaust (108 kb WAV)
Sound from TMWE-treated engine exhaust (108 kb WAV)
(See corresponding microphone signals) |