Strange sounds (stock)
On April 20, 2019, YouTuber 'Dumitru Daniela' posted video footage of strange noises she heard in the skies of Tulcea, Romania on March 20, 2019:
Hi guys! I really need your point of view about this strange noise. There wasn't any sign of plane or helicopter, no wind, no explosion, no asteroid.

She comments that the nearest airport was 16 km from her city and hadn't been operating since 2014. Nobody heard anything from the area of the city's stone quarry either.

The sound was bizarre enough that she notes the effects she saw and felt then:
The strange thing about the noise is that he [it] was going straight ahead and coming back but not 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.