"Are you shouting here?"
Translation:Ti kiabáltok itt?
In this case it is necessary, as the question is aimed at the person: "is it you who is shouting?
If your question is aimed at the activity (are you shouting vs doing something else?), then the personal pronoun is not necessary. In that case the sentence would be said with special emphasis on "kiabálnak" or the word order could als be changed.