The loudest noise ever recorded was caused by the explosion of a meteoroid or comet in the Earth's atmosphere on June 30, 1908, by the Tunguska River in Krasnoyarsk Krai, Russia. It had the impact of a 1,000-megaton bomb with a decibel rating of 300 to 315.
Another loud event in history that did not have the chance to be recorded was the explosion of the Krakatoa volcano in 1883. A barometer located 100 miles away from the incident registered the sound to be 172 decibels. In fact, people who were 3,000 miles away in the Indian Ocean heard the sound of the explosion and attributed it to the sound of heavy guns.