This video has been recordered in center of Kiev, Ukraine on March 12, 2012.
And this time the strange humming sound seems to come from a large construction site.
As added by the uploader of the strange sound video:
[quote_box_center]This video has been captured by my wife in the center of Kiev, Ukraine, on March 13, 2012. Actually it’s just a wind blowing into a big pipe on the construction site which might be seen on the video.[/quote_box_center]