The loudest sound ever recorded on Earth was the result of the volcanic eruption of the Krakatoa volcano in 1883. The explosion was so powerful that it produced a sound wave that traveled around the Earth four times. The estimated sound level was an astonishing 180 dB (decibels) at a distance of 100 miles from the volcano.
To put this into perspective, 180 dB is significantly louder than what the human ear can tolerate. Prolonged exposure to sounds above 85 dB can cause hearing damage, and the sound of a jet engine at close range measures around 150 dB. The Krakatoa eruption was heard over 3,000 miles away, and the sound was described as a series of deafening explosions that rattled windows, caused eardrums to rupture, and was even audible as far as 3,000 miles away in Australia.
It's worth noting that this is an exceptional event, and in typical circumstances, the loudest sounds on Earth are generated by powerful explosions, such as those caused by nuclear detonations or large-scale industrial accidents.