First, let's discuss rhythm.
In stanzas 1 and 2, almost every line has 10 syllables, providing a steady rhythm. In the last stanza, the lines are shorter, mostly 8 syllables a piece. This gives a sort of "drive" to the conclusion. The poet adds further force to the ending by repeating the phrase, "What did I know, what did I know."
Like most poets, Hayden uses alliteration, that is, he uses words that have the same initial consonant sound. For example:
a) weekday weather
b) banked fires blaze
c) love's austere and lonely offices
Hayden also uses a number of words that make us think of sounds: cracked, splintering, call, speaking.