691
Probably bad for your hearing too
(piefedimages.s3.eu-central-003.backblazeb2.com)
For reference, the loudest sound ever on earth was 180dB https://wikipedia.org/wiki/1883_eruption_of_Krakatoa
The decibel scale is logarithmic, meaning that a 20,000 dB sound would carry an unimaginable amount of energy.
A hypothetical 20,000 dB sound would have an overpressure of approximately 5 x 10^499 atmospheres, enough energy to obliterate the Earth instantly.
Just to put this insane pressure scale into context, the core of a neutron star is estimated to have a pressure of 1.6 x 10^34 pascals.
1 atmosphere is 100 kPa, so you'll have to take 5 zeroes off, but when the magnitudes aren't even in the same magnitude, it doesn't really matter.