The peculiar din was so loud that it rattled windows and seemed to last between one and three minutes depending on the location.
It started up at around 8:15pm on Sunday and was reported in several communities across southern Wisconsin including Albany, Evansville, Janesville, Beloit, Monticello and Milton.
Witnesses played down suggestions that it had been an airplane and there had been no thunderstorms reported in the area.
A staff member at the Southern Wisconsin Regional Airport who had also heard the noise on Sunday night revealed that there had been no planes flying through local airspace at the time.
“I heard the sound, too, and there wasn’t any jets flying through or anything like that,” he said. “If they would have came through our airspace, I would have seen it.”
Another possibility, a meteor impact or explosion, was also ruled out by NASA’s Allard Beutel who maintained that there had been no objects tracked over Wisconsin at the time of the incident and that the sound had lasted way too long to have been an object from space.
UFO author and Milton resident Ryan Skinner has also been trying to explain this roar.
“This was constant tone of over two minutes with nothing lit up in the skies,” he said.”The only thing known to be overhead at that time was 747 going to Orlando at 12,000 feet.”
“It was way too high for that noise.”