How would يَسْمَعُ be used for “he did not hear”?

Negating the Imperfect with Lan and Lam: Subjunctive, Jussive and Full Paradigms

• لَنْ يَسْمَعَ
• لَا يَسْمَعُ
• لَمْ يَسْمَعُ
• لَمْ يَسْمَعْ