My leo's not usually bothered by loud noises outdoors when he's indoors - something nearby like the door closing or the cage lid falling tend to scare the snot out of him for a second, but if it's far away it doesn't really faze him.
I was wondering the same thing, living in Holland where everyone is allowed to light fireworks so it is always an ordeal outside. Since I will be abroad this NYE, I figured that it might help to have a cloth put over the cage so they can't see all the lights through the blinds.
for me it will be right outside the window probably, so across the room to the window will be 3 feet. then again, most of it will either explode on the ground or high up in the air and my geckos are on the first floor.
Anyway, there's nothing I can do about it and there are many happy gecko owners in Holland that don't have to buy new geckos every 1st of january
My girls can care less if thier is any loud noise lol nothing gets to them even when the dogs bark or if the T.V is a little to loud. Or even yelling in the house they care less if the noise is in the day time they sleep away nothing scares them.
Mine has never experienced fireworks, but the fire alarm in the apartment we used to live in was ear piercing. She was usually pretty good about that. She would poke her head out when it first started going off like "What the heck is going on around here?", then usually go back in her rock mildly annoyed that it wasn't going away.
I would guess yours should be fine after the initial sound shock and they come to expect the 'annoying sound'. Might want to check on it a time or two just to be sure.