2.5 year old toddler suddenly afraid of noises/ birthdays etc? Should I be worried?

Perhaps it could be the noises that triggers his sound senses and make him shocked/cry/afraid/restless. This happened to my 5 years old when she was young. Any birthday songs, loud voices, balloon pop will make her scared and cry. However, as she grow up it is okay. Should this be a concern please have it check with doctor during assessment to monitor or review.