Listening to those sounds (the ones where i think they are authentic)...i am getting reminded of what i can only describe as "giant industrial floor cleaner". I don't know, somehow i have this in the back of my head although i don't remember from where i remember the "industrial floor cleaner/sweeper" sound...

It's very obvious "mechanical" to me like a giant machine.

As for hot air balloons...we have them occasionally here, even going right over the house.... and they are usually quiet unless they fire..but then it's more like a short whoosh where the balloon is climbing again...i dont think its even remotely the same sound.

i was following this thread before i made an account (been lurking for a long time) and i forgot about it. in mid december i woke up (just barely) and heard the STRANGEST sound. it was very similar to the weird sounds described here. i do have jets that fly over and sometimes they are low. the airport isn't too far from me. this was different and lasted too long for it to have been a jet flying over. there IS a military base here and from time to time i see military helicopters fly over but this was more of a jet sound. the copters are different (though really loud if they are low). had i not gone back to sleep i'd be able to remember it more clearly. i just know it was very different from any other loud engine sound i'd heard.

anyway, just thought i'd add my .02 cents. it was odd and made me think of this thread.

Well thanks for the bump because I want people to stay aware of it. I'll never forget that sound. I've been hoping to hear it again since I now have a better camera, but so far haven't. I am paying attention though and keep the cam close just in case.

I can't believe I forgot to come on this thread and post this, but I woke up three nights ago to the rumbling sound again here north of Memphis. It's been quite a long time since I heard it but it's back.

Stealthy Kat - There are another 4-5 threads on this thing that have popped up in last few days, all the same sort of thing,
Were you mapping the locations of these? It's a shame that people aren't adding to this thread rather than starting new ones every time - it just make it so much harder to follow all the events.
This is happening so much it makes me wonder if there could be a forum for these events alone? Mods?

Also - would he nice if we got a concrete answer on any one of these events because I am sure as yet not one has been given a convert 100% rational explanation? They have been heard in USA, Ukraine, UK, costa rica. Pretty much across the globe,
What we need to do now is collate the times these things are happening as well - because if it's heard at 8am on UK and 2 pm in costa rica(or whatever the time differences are) - is that the same event causing the same sound?
This is the most intriguing thing I have read on this site in years - and whatever I can do to help I will do. At e weekend when I have some time I will try and collate the timing of these events..let's see if there is a pattern of a sort.
Anyone else able to start this before then? And PM me with what threads you have got the info from so far so I can carry on.

Also - where these sounds are heard - airbases, mines, Fracking - what's happening near them
It's a lot of work but come on ATS we have some amazing minds here - let's get to the bottom of this phenomenon