“shofar.” The ram’s horn trumpet, not the metal trumpet.
“in the hill country of Ephraim.” Ehud was from the tribe of Benjamin (Judg. 3:15), but in this record, he went to rally an army from Ephraim. Ephraim was a stronger and more prominent tribe than Benjamin, and that may have been why. Also, we do not know for certain when the war between Benjamin and Israel occurred in which most of the men of Benjamin were killed (Judges 19-21). If it was before this, then the Benjamites would not have been able to muster an army.