Donne is known for his clever wit. That's not limited to his images or his arguments—it applies to they way he plays with sound, too.
Yes, there are three ten-line stanzas in this poem, but really, each stanza can be broken into three units. The first unit is the Petrarchan sonnet stanza, with the rhyme scheme ABBA. Because they are so close together, the rhymes in the second and third lines of each stanza stand out more. They stand out even more because the second line is so short—it collapses the distance between rhymes. In a way, this all makes perfect sense, because some of the most important lines in the poem occur here. The rhetorical questions "Why dost thou thus?" and "Why shouldst thou think?" provoke the whole argument of each stanza. Line 22 has the poem's most blunt line, "Nothing else is," which sets us up for his strongest and most elaborate claim—that the world has ceased to exist outside his room. By shortening and drawing strong rhymes to these lines, they carry more force.
The second unit is the Shakespearean sonnet quatrain, which has an alternating rhyme scheme of CDCD. This rhyme scheme de-emphasizes the sound effects by spreading out the rhyme, making it easier for us to focus on his imagery. Which is good, because it takes a lot of our energy to keep up with his logic. Donne uses the English sonnet stanza to take the pressure off the sound and extend his argument more easily.
The final unit is the couplet, two rhyming lines. Couplets have been around for a very long time, but at the end of sonnets (especially Shakespeare's) they usually have a certain ring—a sense of closure or resolution. That's just how the rhymes operate here. They wrap up all the craziness of the stanza and explain it distinctly and directly.
Another sound effect in the poem is the reversed iambic foot. No, that's not a wrestling move. The whole poem is iambic, meaning it has that unstressed-stressed daDUMdaDUMdaDUMsound: "I could eclipse and cloud them with a wink." Every now and then, though, Donne breaks that pattern. That's not too unusual—it would be really boring if it stayed perfectly iambic all the way through. But it's where he changes it that counts.
It's usually at the beginning of the line and often at a particularly strong word. Look at the first word: "Busy." Listen to it: the stress is on the first syllable. Not only that, the "B" sound explodes out of your lips ("P" and "B" are known as plosive sounds for a reason). So Donne sets the tone and grabs our attention right there at the beginning. Other reversed iambs (actually called trochees) can be found in lines 9, 16, 21, 22, 25, and 29. Look back at each of them and see if you can tell why Donne might call attention to those words. There are a lot of possible answers.
The other overall sound pattern in the poem is in the consonant sounds. In the first stanza, Donne emphasizes his griping anger with lots of harsh sounds—R's, K's, T's. Look at line eight: "Call country ants to harvest offices." By the end of the poem, though, he's mellowed out into softer consonants: L's, M's, N's, and W's.