What is the meaning of "El Chikecha Shofar"?
Rashi: The Shechinah tells the Navi to make heard the voice of his palate and call like a Shofar, as if a Shofar is in your palate.
Radak: This is like it says above "Tik'u Shofar ba'Giv'ah" (5:89). When it addresses the nation, sometimes it uses the singular, and sometimes the plural. Put the Shofar to your palate, for "ka'Nesher?" One puts the Shofar to his mouth; the verse mentions the palate, for the voice comes via it after leaving the throat.
Radak citing Targum Yonasan: Navi, call with your palate when the Shofar?
Malbim: Hashem tells the Navi to put the Shofar to his palate, rush to fly like an eagle and stand on Beis Hashem and sound the Shofar. They would sound the Shofar in Beis Hashem for a great matter and announcement. He will stand on Beis Hashem, at its height, so people will hear the Shofar in all ends of the land. Also, it is so Yehudah will hear and return to Hashem in the days of Chizkiyah, when Melech Ashur besieged them. Hashem rushed like an eagle to save His nest ? "k'Tziporim Afos Ken Yagen Hashem Tzevakos Al Yerushalayim" (Yeshayah 31:5).
What is the comparison to an eagle?
Rashi: The enemies will fly quickly like an eagle and come to Beis Hashem.
Radak: The enemies will come to Eretz Yisrael, and also to Beis Hashem to destroy it, "because they transgressed the Bris." [Yisrael] abandoned [the Mikdash] first ? also I will abandon it, and leave it in the hands of strangers.
Why does it say "Ya'an Avru Brisi"?
Malbim: He must inform that the evil comes to them for transgressing the Bris and Torah.