The strange sounds phenomenon is being recorded again and again. Here some videos recorded in Tulcea, Romania and Kurseong, West Bengal, India.
Strange Sounds from the sky in Romania
This video of a strangenoise was recorded in Tulcea, Romania on March 20, 2019. According to the uploader there wasn’t any sign of plane or helicopter, no wind, no explosion, no asteroid. The nearest airport is 16 km away and had not been operating since 2014.
The strange thing about the noise, she explained, is that it was going straight ahead and coming back but didn’t rise up… and more than that, the sound was so powerful like you could feel the vibration of it, like when you are staying next to a speaker.
Strange Sounds from the sky in India
This weird noise from the sky was captured on May 1, 2019 over Kurseong, West Bengal.
 What’s being speculated online
Tectonic plates grinding – Tectonic plates are pieces of the Earth’s crust and uppermost mantle, together referred to as the lithosphere. The plates are around 100 km (62 mi) thick and consist of two principal types of material: oceanic crust (also called sima from silicon and magnesium) and continental crust (sial from silicon and aluminium).
Atmospheric pressure – Atmospheric pressure is defined as the force per unit area exerted against a surface by the weight of the air above that surface.
Trains shunting – Self explanatory – noise comes from trains in reaction to the track and overhead wires.
Construction – Building works, especially if going on at the same time across a specific area, can led to similar sounds.
Aliens – Can this be an alien lifeform in the sky, perhaps scouring out Earth?
HAARP weapon – Rumours persist that the U.S. government uses secret weapons in the sky for defence and weather modifying, the High Frequency Active Auroral Research Program (HAARP). This wouldn’t explain the sounds in other countries however…
The Apocalypse and the Seven Trumpets of Heaven – Seven trumpets are sounded, one at a time, to cue apocalyptic events that were seen in the vision of the Revelation of Christ Jesus, by John of Patmos. Somewhat more worrying as it would signal the end of the world…
Not so strage.
In Romania, in 2008, was similar sound hear in tha capital, Bucharest.
https://www.youtube.com/watch?v=M-KZ68BxED4
I have one more theory.
In some part of industry periodically have release of presured air.
The condition was favorable for echoing that.
Keep calm! 🙂
PS over the world are another strange sounds that I can’t explain, like this> https://www.youtube.com/watch?v=VSKcyBCAR-4