We can't really base the sound of this poem off the English translation (sound is very particular to each language). So we suggest you listen to the poem in its original language to get a sense of how it sounds. Still, there are some pretty obvious sounds that are carried over into the translation. For example the "o" sound that repeats throughout (in both the Spanish and the translation) is a very soothing sound (think "ommm"); this adds to the sense of comfort and intimacy that the poem conveys.
Another important aspect to the sound of this poem is the pauses. You'll notice that there are a lot of commas (which usually indicate a pause) even in the middle of lines. If you read the poem out loud, you'll find yourself pausing as you would in normal conversation – that is, often, and without regularity. Once again, this increases the sense of intimacy: it's as if we're listening in on a private conversation (or one side of it, at least) between two lovers.