Low freq sound of nature?

The sound is in range approx. from 25 to 50 Hz and it was the third time I heard it..It came in a few "waves" with a break of about 5 - 120 seconds between each other,,,,,.I were out with my friend when it repeatedly came...I decided to capture it....it was very quiet ( the noise of the record is caused by capture device (SE C 702 ) ..sound is volume-edited....It doesn't seem to be any explosion or engine.....it was something like a waves of the vibes comming from under the ground far far away...but nothing was shaking.....only the sound....//Also I heard it 2 years ago on the hill approx. 3-4 kilometers further and 700 meters higher than this record spot(and also further away from the source of that sound) ...so it must be something really huge.......It's happening mainly in the morning and around the noon...I have never heard it in the evening or night......Warning...the sound is available to hear by subs, big speakers, or really good headphones(available to reproduce the low frequency sound) only ...Turn the volume up

Category:

Travel & Events

Tags:

• Low freq sound
• nature sound
• vibes
• under ground