I'm wondering if not fearing noises is a basenji breed trait. I have two basenjis, and they've never shown fear of loud noises.

Fireworks in my neighbor's backyard? No reaction.
Thunder? Not a reason to move.
Gunfire? No issues (it was 20-30 yards away on a few occasions).

They do startle (e.g., when they are simply sitting in the kitchen, minding their own business and a dish full of food falls off the counter and breaks). However, it seems more like the motion of a close-passing car or falling object that startles them, because sound alone seems not to. Do you think it is my individual dogs, or the breed generally?