[Glenn Wright]

I like the first half of this poem very much, but I found myself tripping over the clunky polyptoton of “articulate/inarticulacy.” The grammar is a bit fuzzy in the last four lines, too.
It might bring it into focus if you use a series of present participles to hold the end together— something like
. . . I didn’t know
she wasn’t listening to the words
but only feeling the quiver in them
and how eloquent the trembling voice
speaking for the muteness of the heart.