Unexplainable "Sky" Noise in Edmonton. (Sept 1st)

A little map to show the distance between the two points where the sound was confirmed by my husband and I.

I was thinking maybe it was some type of industrial generator since the sound was a constant tone.
Seems like that would be pretty easy to find though since more equipment would probably be present as well. The pumper truck seems like a pretty viable guess. If you guys have a local Public Works Dept you may check with them and see if they had some sort of emergency in your area. Were there any power outages at the time around your area that night ? Maybe a utility company working on power lines, but again it seems like that would be pretty easy to find.

That's about all I can think of

Looking at the map of your area I couldn't tell if there were any large stores or shopping malls in the area... The sound very well could be a parking lot vacuum truck... The ones I have seen are always after business hours late at night or early morning hours... When I was single I would go shopping at a Wal-Mart super center or Krogers at around 2 or 3:AM when the parking lot was being swept... There is a separate engine on the truck that powers the vacuum's large turbine type fan that runs at a constant RPM... There is one thing I forgot about what you posted.. It was raining.. I don't know if they operate Vacuums like that when it rains but I do know that shop vacs that are used wet or dry are louder when picking up liquid...