1)
What is the significance of hearing the Shofar?
1.
Radak: The Navi's word is like the sound of the Shofar ? "ka'Shofar Harem Kolecha v'Haged l'Ami Pish'am" (Yeshayah 58:1).
2.
Malbim: (a) There are Simanim in blowing the Shofar. One who understands the Simanim knows which side to flee or how to be saved ? "v'Shama ha'Shome'a Es Kol ha'Shofar." If he did not heed it, Damo b'Rosho. Also refer to 33:5:1:1.
2)
Why does it say "Damo b'Rosho Yihyeh"?
1.
Rashi: The sin of his death he will seek for himself ? he sinned against himself.