Why is my son afraid of loud sound and mascot or statue?

I have a 4 year old son. Every time we went to the mall or church he always feel uneasy and afraid of sounds from a loud speakers specially if there are instruments such us drums. I love parties, my friend always invite us of their children birthday party. But my son always cried because of the clowns and mascots. He is hysterical and he just run out of the party. I was very worried about the behavior of my son. Please help me.