The loudest recorded sound?

The loudest sound recorded in the annals of history if not recorded on actual audio gear was apparently the 1883 Krakatoa volcanic eruption according to Aatish Bhatia’s fabulous article.

Some outtakes:

• The sound was 172 dB SPL 100 miles away based on a barometer measuring the pulse at 2.5 inches of mercury
• Sound waves (the compression and rarefaction of the atmosphere) top out at 194 dB SPL, in the Earth’s atmosphere, because at that SPL rarefaction leads to a vacuum, the limit of what is possible. Pressure waves above 194 db SPL simply push the molecules around and are considered shock waves.
• The sound continued to reverberate around the globe (as measured by instruments) at roughly 34 hour intervals (the time required for sound to circumnavigate our planet.
• The sound was observed by people up to 3000 miles from the island of Krakatoa

Aatish includes a link to a video recording of a relatively small eruption where the observation of the eruption was followed by a visible expanding shock wave with the over pressure eventually hitting the camera and the folk recording.

A list of high SPL sounds for comparison.

The story is not simply a curiosity but also a great tragedy as over 100,000 people may have perished in the eruption and resulting tsunami.