Final answer:
Whitman's line features alliteration, a poetic device that involves the repetition of consonant sounds, rather than simile, metaphor, or rhyme.
Step-by-step explanation:
The line from Walt Whitman's poem 'Song of Myself': "I sound my barbaric yawp over the roofs of the world" uses alliteration, which is the repetition of consonant sounds at the beginning of words. In this particular line, the alliteration is not immediately evident; however, Whitman's poetry often plays with sound and rhythm in broader contexts. While simile uses a comparison using 'like' or 'as', metaphor directly equates two things for symbolic effect, and rhyme involves matching ending sounds in different lines, this specific line does not utilize any of these three devices explicitly. Instead, it is Whitman's use of language, tone, and the non-traditional structure of his poetry that holds the essence of poetic devices.