OK, I know there are plenty of islands out there that have been formed by volcanoes (just look at Hawaii for one prime example). So what's so special about Krakatoa?

Fine, it's not like I've orchestrated a contest between volcanoes to see who could make the loudest, angriest sound. But in this instance, someone did record how strong the explosion one. And by someone, I mean many people...
August 1883: Krakatoa explodes in a series of violent blasts, bringing down tens of thousands of humans and countless animals. Its lava extended to neighboring islands, destroying all in its passage like a voracious monster. The eruptions were so loud one was heard 4800 km away, across the Indian Ocean to eastern Africa (a distance which took the sound wave approx. 4 hours to travel), while others were heard off the coasts of Australia and Southeast Asia.

But you know what the scary part about all this is (if this wasn't scary enough)? Krakatoa isn't a supervolcano...
Source:
Historical eruption sounds