What are the "Kol Shemu'ah" and "Ra'ash Gadol"?
Radak: The noise that we hear, and the frightening reports like an earthquake.
Radak (22, 23 citing his father), Malbim: We heard that Nebuchadnetzar left his place. This was the Kol. We did not hear to which place he will come. Malbim - it says in Yechezkel (21:24) that Nebuchadnetzar left his land and was at the crossroads, and cast a lot to decide if he should go against Amnon or Yerushalayim 1 . The lot fell on Yerushalayim. The Navi saw this (Radak - he will come to make Arei Yehudah desolate), and prayed that he go against Amnon instead.
Radak: Nebuchadnetzar planned to attack Amnon. Hashem caused him to change, due to Tzidkiyah, who transgressed his Shevu'ah, which was Chilul Hashem.
Why does it say "Ba me'Eretz Tzafon"?
Radak: Refer to 10:22:1:2.
