I have heard a strange low rumbling sound which sounds like an aircraft, but lasts quite some time, and never any aircraft visible. I live in Cumbria.
I am going to answer your questions from your OP, to the best of my abilities.
Originally posted by technologicalsingularity
1.Are you near a highly protected base when you heard these sounds?
There are Army bases nearby, I wouldn't say they are highly protected. Sellafield nuclear re-processing plant however is highly guarded with AA guns,
2.Are you experiencing unusual weather, when the noise can be heard?
No, I have heard it on windy days and calm sunny days.
3.Is it daytime or nighttime when you heard these sounds?
4.Where you heard these sounds, do you have frequent chemtrailing?
Chemtrailing is a hoax, if you are referring to aircraft contrails, then yes, we have them often.
5. HAARP rings?
HAARP is a research program designed to study the ionosphere in an attempt to improve radio signals and research, I don't see how that would make a
6. Do you live near an oil refinery?
No, however my town (like many towns in the North of England) is built on top of miles of old mine shafts.
7. After sound has gone, can you see iridescent trails and cloud disturbances in the sky?
Can't say I have ever noticed, but then it's Cumbria, it's cloudy 90% of the time, lol.
8. Any recent or happening earthquakes?
The was a 4.0+ EQ not that long ago, centered under one of our lakes, first time I ever felt an earthquake, I just thought it was a large truck going
9. Do you live near a volcano - active, dormant or extinct?
Yes, Cumbria, like most of the UK, is full of extinct volcanoes.
Hope these answers are of some use.