If we had a keen vision and feeling of all ordinary human life, it would be like hearing the grass grow and the squirrel's heart beat, and we should die of that roar which lies on the other side of silence.
- George Eliot, Middlemarch
What's up with the epigraph?
Without ever saying Noise, the epigraph is a shout-out to the experience of constantly hearing everything. Being tuned into every human thought is akin to being tuned into every sound in the world, and Eliot's point in Middlemarch is that this experience would completely overwhelm us—in her assessment, to the point of death.
While people in The Knife of Never Letting Go who have Noise are decidedly alive, a metaphorical death of sorts has taken place in Prentisstown. All the women have been killed and Todd is the last child left in a community of men, all of whom have become men by passing through a coming-of-age ritual that involves murder. So while the inhabitants of Prentisstown are technically alive, life as they once knew it is most definitely dead. This is a new society, one established "on the other side of silence" and governed by the "roar" that exists there.
And that, Shmoopers, is what's up with the epigraph.