Great question! Ideally the high decibel sound in the movie hall is not good for babies. Try plugging cotton in your baby's ears so that atleast baby can sleep if he wants. Yet if it is the first time and baby gets scared, you might have to leave early. Don't get disappointed if that happens.

Not so soon let him complete 3 years ,than you can take him because at this age they won't allow you to see or they won't see they ears are so tender the loud sound may effect their ears .