Stick with fireworks, explosives are bad, unless you have a stump that needs removing. ;) They have this nasty habit of taking fingers, eyes and ears when they go off. :P

I once set off a quarter tin (maybe 1/8lb) of gun powder with the tin inside a sealed wooden box. I was about 50ft away and still couldn't hear for about 2 days. His was about a backpacks worth wrapped up to maximize the explosion. I think it was plenty loud.

I've got to say, I like Mat's solution better.

He climbed in. Mat actually sees someone that could have been Rand, either that or some random Aiel.