The most significant sound in "Power" is the sound of silence. (Cue Simon and Garfunkel.)
No, really, folks. Notice all those long spaces between words? When you read 'em out loud, you've gotta pause. And pause for quite awhile.
All these pauses make the poem sound choppy and jumpy, even a little herky-jerky. And this is especially true at the end of the poem, when we begin to hear about Marie Curie's death. All those absences, that we read aloud as silences, create tons of little pauses—little voids of emptiness—in the poem. "Power" is not smooth sailing; it's sailing on some pretty darn choppy seas.
And, now that we think about it, navigating power itself is like sailing on some pretty darn choppy seas. Coincidence? We think not.