Strange and mysterious sounds “hum of the Earth,” March 13, 2016

Night hum
March 13, 2016, the city of Drogheda in Ireland

Something very creepy going on outside is it a ufo 
Опубликовано Mary Ann Kinsella 13 марта 2016 г.

Further, not March 2016, the case of 2011.
A strange sound and anomalous flash in the sky.
Location: a small lake to the west of Alexandria, Minnesota, USA.
Date: September 25, 2011
During the 4 minutes, the witness heard a strange sound, so he was on the boat and rowed it is not immediately able to record video, after a bright flash in the sky the sound stopped.
Flash on 1:16.

description of the author of the video

This happened on September 25th, 2011 at a small lake West of Alexandria, MN. It took me a few weeks to get time to put it on YouTube. There was a constant humm/rumble for around 4 minutes and I got my camera to film it because it was so odd sounding and rattling my aluminum row boat. The sound changed slightly and then there was a flash and the sound faded away. A guy across the lake heard it too and he thought it was a transformer blowing up but he didn’t see the flash. I saw nothing in the news so I thought I’d post this to see if anyone knows what it was. I thought it was something military related. Please don’t copy this video, I’d like to get the answer here and not miss it if it’s posted elsewhere. It was around 2pm, sky was very cloudy but no rain or thunder/lightning.