The "quietness" in this poem is complemented by an emphasis on sound and hearing. There's a whole section in the middle where the speaker tells us what it's like to hear the woman's name spoken in his presence (hint: not good). It is by means of the ear—by hearing—that the speaker stays connected to the outside world without slipping completely into the world of silent, solitary grief that occupies most of the poem.
Lines 15-16: The speaker mentions hearing a name—that of his estranged friend. To "hear" the name, however, is kind of like admitting one's guilt. To "share" in the "shame" is to imply one is part of the cause of this woman's shame.
Lines 17-18: The speaker compares hearing the woman's name to hearing a "knell" (the bell rung to announce a death). This is a metaphor that gives us some idea of how painful hearing this woman's name is. It's like being suddenly told somebody has died. Or rather, it reminds him that a part of him is dead, or a relationship he once had is no more. You get the idea.