Hearing the shofar rebuilds doing

לשמוע קול שופר עיקר המצוה השמיעה כמ"ש ברא"ש וטור.

"To hear the sound of the shofar" — the essence of the mitzvah is the hearing, as the Rosh and the Tur write.

The blessing is "to hear the sound of the shofar," and the halachic authorities establish that the mitzvah lies in the act of listening, not in the blowing itself.

וי"ל ע"פ המדרש קלקלתם נעשה הזהרו בנשמע כו'.

And one may explain this according to the Midrash: "You ruined 'we will do' (naaseh); be careful now with 'we will hear' (nishma)…"

The Midrash says that since Bnei Yisrael damaged the level of "naaseh" (doing) through the sin of the Golden Calf, they were told to be especially careful to guard the level of "nishma" (hearing).

כי הקול לא קלקלו שהוא מקום גבוה יותר וקיים לישראל לעולם כמ"ש הקול קול יעקב.

For the "voice" they did not ruin, since it is a higher place and endures for Israel forever, as it is written, "the voice is the voice of Yaakov."

The deepest level — the "voice" or "hearing" — was never damaged by their sin, because it stems from a higher source that remains permanently intact for Bnei Yisrael, the eternal "voice of Yaakov."

וכ' עושי דברו לשמוע כו'.

And it is written, "those who fulfill His word, to hear…"

The pasuk (Tehillim 103:20) speaks of "those who do His word, to hearken to the voice of His word" — placing doing before, and as preparation for, hearing.

ולזאת עכשיו מצפין ע"י שמיעת הקול לבוא למעשה שהוא הדיבור כמ"ש עושי דברו כו':

Therefore now we hope, through hearing the voice, to come to action — which is the "speech" — as it is written, "those who do His word…"

Since "doing" was damaged but the "voice/hearing" was not, we now begin with the intact level — hearing the shofar's sound — and use it as a springboard to restore proper action and fulfillment of Hashem's word.

Summary: The mitzvah of shofar is specifically "to hear," because while Bnei Yisrael damaged the level of "naaseh" (doing) at the Golden Calf, the higher level of the "voice" — the eternal "voice of Yaakov" — was never harmed. We therefore begin from this intact level of hearing the shofar and use it to rebuild and return to proper action.