WINDSOR, Ontario, Aug. 25 (UPI) -- Canadian environmental sound detectives are looking into a mysterious humming sound and vibrating effect in the border city of Windsor, Ontario.
Ontario's provincial Ministry of the Environment has received more than 300 complaints since March about the phenomenon that residents describe as a low-level, throbbing hum in the evening, the Detroit Free Press reported.
As a result, the ministry has set up seismic and sound monitors, but there hasn't been any official word on what's been recorded.
Resident Dave Robins told the newspaper the nightly event was hard to ignore.
"It sounds very similar to having 50 Mack trucks idling outside your house," he said. "It sometimes makes the windows vibrate."
Since the humming began in March, theories of its source have abounded -- from underground detonations in area salt mines to industrial noise from Detroit across the river, the newspaper said.
There have been no similar complaints from Detroit residents, the report said.