The sound of "The Computation" is centered on the five distinct couplets (two lines). There is not enjambment in this poem at all, and the only example we can find is the transition between lines 9 and 10. But there are especially big pauses after each couplet. These pauses help to create a sense of more and more time passing, even though a half-second pause doesn't compare to a thousand years. But that's why we have imaginations. And Donne knows this. Each couplet introduces a larger time period, from twenty years to forty to hundreds of years to thousands of years and, finally, immortality, the longest period of all. So, after every big pause, the sense of time becomes a little more absurd, until finally the speaker calls himself a ghost.
The poem's sound is also defined by an interesting sense of rhythm. The poem begins with two anapests (two short syllables followed by a long one – da-da-DUM), and this rhythm is often compared to galloping. Donne must have wanted to start the poem with a sense of acceleration, like a horse charging out of the gates at the Kentucky Derby. The poem finds its groove with an iambic pentameter (see "Form and Meter" for more), but it slows down at the end, as if to mark the fact that the speaker is removing himself from time altogether. The last two lines contain several caesuras, or pauses within the line that slow down the reader.