[metadat]

If planes, with active propellers or jet engines, are only audible for a diameter of 20-50km around the vehicle, how could a falling unpowered ring of metal be audible from 200km away as per TFA?

[jcims]

It would have been supersonic at a very high altitude and likely came in at a steep angle, so sonic boom + large exposure area + long path.

[zardo]

While it was supersonic it would have produced a sonic boom all along it's path of travel.

[MR4D]

Sonic boom(s). Unsure what the speed is, but could have been significantly higher than terminal velocity at sea level.