It is spelled ligygrophobia.
It is the fear of sudden loud noises. This can include, the popping of balloons, and most definitely firecrackers and fireworks. But it is really just the fear of any sudden, loud noise. Sudden is the key. Anything that startles can send a person with ligygrophobia into a panic attack.
I myself suffer from this and I am afraid of guns, balloons popping( although I've kind of gotten used to balloons because I have a 3 year old who loves them) and firecrackers and fireworks. I wear ear plugs on July 4th and any other time there are going to be fireworks. If I see anyone with a gun, I have a hard time not turning tail and running away.
I carry ear plugs with me all the time.