Question

I have a recessed window above my stairs and I get alot of noise from the outside coming in. My problem is I have a real problem with the fireworks loud noises coming through this window and the wall. I have to make this window and wall as soundproofed as possible and as inexpensively as possible before Saturday the 4th of July because other wise I am going to have alot of noise in here. I live alone so trying to get to the recessed window might be a problem but maybe there is something you can suggest I can do. I would have liked to have hung a soundproof curtain but I can reach to put up a tension rod in the recess it is too high. Is there someting I can put up temporaily maybe across the bottom of the window.? I tried taping a couple of pieces of heavy poster board together and running them on the sill of the window but they did not help they only went half way up the recessed frame noise still got in. Please help me if you can....It has to be very cheap to do....