So why does it make the noise?
As i understand it, the wick is so well saturated that when the (ideal) vaporization process begins it essentially forms a bubble inside the liquid that's present on the wick, and when the bubble escapes it essentially "pops" with almost explosive force. Certain types of juices (high PG) and coils builds (specifically parallel) will make it much more prevalent.
A hilariously disgusting simplification would be to imagine farting in a bathtub, when the bubble reaches the surface and "pops" that's essentially the same thing thats happening in the atty, but with a bit more force.
Again AFAIK, but it usually means your setup is working well.
