Balloon popping can be so loud and startling that there are people with serious phobias of balloons. That's understandable, after all: hearing a balloon pop is alarming and upsetting even if you know it's coming. Just looking at a balloon with a pin near it, or watching someone inflate a balloon too much, can give someone feelings of anxiety.
But... how much of that noise is actually from the pop, and how much of it comes from the noise bouncing off walls? These guys went into a room with padding on the walls that absorbs echoed sounds and tried it out.
Wow, that's a BIG difference.