Reading "The Broken Heart," you might expect that the most common sound effect would be the heartbroken sobs of the speaker, or maybe the mournful honking of him blowing his nose into his handkerchief. Since we're dealing with a master like John Donne, though, this poem actually offers up get a whole lot more to listen to.
Take, for instance, all the consonance we have going on in this poem. Repeated consonants echo throughout the poem's lines, as in the S sounds of "Yet not that love so soon decays,/ But that it can ten in less space devour;" (3-4), which emphasize the quick-moving, snake-like speed of love's emotional devastation. We also get D sounds in "By him, as by chain'd shot, whole ranks do die;" (15). The added alliteration of "do die" really drives home the dull and driving thuds of love's blows against us poor mortals.
We get more consonance in lines like the T sound repeating in "Mine would have taught thine heart to show" (22), and the TH sounds in "Therefore I think my breast hath all" (27). Finally, we have more S sounds returning towards the end of the poem: "And now, as broken glasses show/ A hundred lesser faces, so" (29-30).
So why do we get all these consonants repeating? One answer is that this technique tends to give a bumpiness to the lines, a jarring kind of repetition that seems totally appropriate for a speaker who is explaining to us just how his life has been totally destroyed by love. Instead of a lot of light and airy alliteration or even assonance , we're instead treated to a hailstorm of forceful consonants in "The Broken Heart," reminding us that love can be a rough ride indeed.