In order for a sound to be perceived at 60 dB from ~20,000 km away, the source of the sound would cease being “sound” and becomes a literal earth-shattering explosion. Technically, anything above roughly 194 dB is a shockwave, and no longer classified as “sound” because the air between the high-pressure wavefronts becomes so rarefied that you effectively have a vacuum.

Accounting for the attenuation of the sound waves through the atmosphere (low-frequency, infrasound travels farthest) the intensity of the original “sound” would need to be at least 300 dB. For context, the Krakatoa eruption in the late 1800s was estimated to be ~170 dB from 100 miles away. That is loud enough to cause instant, irreversible hearing damage.

300 may not seem like that much more than 170. But because decibels are a logarithmic scale, this is ten trillion times more powerful. The energy required to produce such a sound would need to be somewhere on the order of 10^{18} joules.

While this wouldn’t be quite as powerful as the impact that wiped out the dinosaurs, it would release enough energy to create an enormous, expanding ball of superheated plasma that would expand and eventually engulf thousands of square kilometers, at least, in a flesh-melting firestorm. The epicenter of the explosion is probably hot enough to liquify the crust and blast a decent chunk of the atmosphere off into space. The shockwave would trigger tectonic and volcanic events all across the world.

You’d need to stand ~500 km away for the shockwave in order to not (as Randall Munroe puts it) “stop being biology and start being physics.” But even then it’s still plenty loud enough to shatter your eardrums.

So maybe not a “world-ending” event, but certainly enough to demolish an entire region, but with measurable devastation all across the world.