New cartos (or atties for that matter) are a little hotter (and make more sound effects) than they are when they've been in use for a while. (Build up on the coil cools them down just a little bit.)
Recently filled cartos generally have a little extra liquid on the coil (which also means more snapping), and after a couple of drags, they get to "normal" levels (less noise.)
And of course, newly charged
batteries are a little stronger, and again give you more noise.
As long as you get the vapor you need, don't sweat the noise. If you're not getting the vapor you want, think about: More power (upgrading battery), lower resistance (different carto or atty) or just keeping the whole thing cleaner . (Change cartos more often, clean atties.)
Best,
ANde