I've killed a good number of birds with body shots and head/neck shots (different broadheads for each method), and I've learned first-hand that the sound of the arrow at impact almost always indicates the quality of the hit.
Poof? It means you attempted to hit the heart/lung area of a turkey, or perhaps another vital area, but your arrow hit either too low or too far forward. Your broadhead clipped mostly or only chest feathers; not good.
Thwack? Chances are decent you'll be tying your tag to a turkey.
Here's to hoping you hear Thwack! on your next longbeard bowhunt!
Until next time . . .