Sounds like Conspiracy Spirit

A trending topic on many social media sites today is "strange sounds." Supposedly, people all around the world are hearing and recording weird sounds coming from the sky. Some are suggesting it's the Earth "groaning," others say it's aliens and others think it's just a viral ad campaign for an upcoming movie.

One of the primary Youtube videos about these sounds, oddly enough, is from Manitoba: http://www.youtube.com/watch?v=AxSulCgmJJA 

Thankfully, Redditors have dug around and found some suspicious similarities between all the videos (a list of which is linked in here), and it looks like it's a hoax or a viral conspiracy theory: http://www.reddit.com/r/AskReddit/comments/oixhc/what_the_hell_are_these_noises_being_heard/ 

One Redditor did some analysis of the videos and posts his comments in the thread, then later in the thread another Redditor posts his check into who's posting the videos.

Conclusion: much ado about nothing. It's not HAARP, or aliens or Gaia. Seems like it's just the conspiracy crowd at it again.