As a kid, I was phobic of both (balloons popping & fireworks). To me it was the unexpected bang of both and the loud sound. Indoor balloon popping and outside fireworks to me were both very loud and unpredictable. As a kid, I decided to overcome my fears. The embarrassment of being scare of these common items was a large factor in pushing me. I tackled balloons first, for me it was easier. After getting a handle on balloons, I started to watch fireworks shows from a great distance. I couldn't be close to fireworks. By late teens, I finally did the deed and bought some firecrackers and set them off. I enjoy popping balloons & fireworks as often as possible (especially with my wife). And no, she doesn't feel the same as I do on popping. BTW, shooting guns were never really an issue growing up. Yes, I know gunfire is louder than either balloons or firecrackers popping. But hey, a phobia is not rational.
/Popper