The old man had been whispering to Cammie all day. He’d started at dawn. The field, illuminated by the frosted gold of the sun’s rising, was just becoming visible at her fingertips when she felt a slow hum building. It was like crickets singing, so familiar she barely noticed – and she certainly didn’t say anything. After all, this was the first spring Cammie was old enough to help with the planting, and she was doing her best to seem grown-up. Mother always said to stop making things up, to stop being so childish, and she hated it when Cammie talked about the sounds she heard. So Cammie ignored the lazy song in the back of her skull and half-walked, half-bounced, tossing fistful of seeds that disappeared in the dusky morning. She tried her hardest to throw them just like her Mother, who produced such a pretty fan-shape with each casual toss. But the hum became a buzz and the buzz a whine, and then he was there, his breath against her ear and his words only half heard, as though a wind caught at his whispers and pulled them away.
I like the motif of whispering.
Notice that you go from a very specific moment-- this dawn, these whispers-- to a general time, not even "today" but "this spring". I think you're trying to cram too much into the first paragraph. You know, really, all you need to do is make it interesting enough that the reader goes on to the next paragraph--- you don't have to shove all the backstory in there. :)
So take it slow. Think of what the central idea of this paragraph is-- the old man. Whispering. This dawn. Not other people. Not other whispers. Not other times. NOW. If you want to talk about something else, start a new paragraph. You lost me as soon as you went from the specific to the general, from "right now" to "back then." There's a time for "back then," but it's not in this paragraph. So let's cut off all the non-whisper/non-now stuff and concentrate on the moment:
The old man had been whispering to Cammie all day. He’d started at dawn. The field, illuminated by the frosted gold of the sun’s rising, was just becoming visible at her fingertips when she felt a slow hum building. It was like crickets singing, so familiar she barely noticed – and she certainly didn’t say anything.
See how you're making "right now" be retrospective? "The old man HAD BEEN whispering"-- past-perfect (had) tense is often a sign of retrospective narration. There is a place for retrospection, sure, but is it here? You're kind of telling the reader, "The interesting stuff has already happened, and I'm going to start after that." You don't want to tell the reader that. :)
Make this moment a special moment. It might be when the whispering starts, or it might be when the whispering suddenly stops, or it might be when she reacts to it or realizes what it was-- I don't know. But NOW is important, isn't it? You're starting NOW because it's important, right? So where does NOW start?
Let's say it's when the whispering starts.
The old man started whispering to Cammie at dawn.
Immediate, right there.
The field, illuminated by the frosted gold of the sun’s rising, was just becoming visible at her fingertips when she felt a slow hum building. It was like crickets singing, so familiar she barely noticed – and she certainly didn’t say anything.
Notice you have several sonic events here-- the whispering, the hum, the crickets. The latter two are apparently what the whispering is like. But we don't know what the whispering is, and the hum and crickets references don't help, because they don't sound like each other, and they don't actually sound much like whispering. Oddly enough, the best metaphors are often unrelated to the object being compared-- because if they're related, we can't really get the metaphor. We're thinking, "But a hum doesn't sound like a cricket. Cricket songs are high-pitched."
I'm not sure which the whispering is like, but I'd choose one of those and go with that. A whisper that is like a low hum would be low-pitched, throbby, seductive, sleepy. A whisper that is like a cricket song would seem to me to be high-pitched, scratchy, exciting, anxious. Which is more like this old man's whisper? I can't get much of an emotional sense of this because those two comparisons each take me in a different direction. Be aware of the signals you're sending, and send the ones you want the reader to get. :)
The field, illuminated by the frosted gold of the sun’s rising, was just becoming visible at her fingertips
I like the sound of this but had to read it a couple times before I figured out what you meant was at her fingertips. Why fingertips? She's planting? Okay, but you know, this is visual, and it might be messing with the coherence. Can she SEE the old man? Or just hear him? Think about sticking with the aural perception for a few lines, and then switch to the visual, but connect it with action. For example, if I heard someone whispering at me, I'd turn and look. There's your visual cue. She turns and looks for the source of the whispering, and the dark is lightening and the sun rising-- if you want to make this immediate, let her provide the cues for what is perceived and what isn't.
Also -- minor point-- you might slip in some adjective before "field"-- the strawberry field, the cornfield? Just to give us a bit more info.
I'm not clear on whether there really is an old man or if she's imagining him. If he's not there in physical form, how does she know he's old? What quality in his voice or what he says makes her think that?
You don't have to address all this at once, goodness knows, but just be aware that the reader will be asking, and that's a good thing. :) But what is he saying? Can she tell?
What is her emotional reaction? Is she scared or not?
It was like crickets singing, so familiar she barely noticed – and she certainly didn’t say anything.
"She barely noticed..." way to diminish the importance. :) At first she barely noticed? I can believe that-- there's this sound, and it's not too intrusive (a whisper, not a shout), but as time goes on and it doesn't shut up, then she notices?
and she certainly didn’t say anything.
This is intriguing, because it suggests that she might be ashamed or worried or something-- that if others knew she was hearing it, they'd disapprove somehow. It also indicates that she thinks no one else hears it.
As a matter of fact, in a town north of me there's something called "The Hum." (Google Kokomo Hum.) Some people in town heard this constant hum, and it made them sick, and other residents couldn't hear it and thought the hearers were crazy. (There actually was a hum-- two big industrial fans.)
It's a great idea for individualizing her right off. She's the one the old man whispers to, or she's the only one who hears him whisper.
But you might say WHO she doesn't say anything to-- her mother? Everyone?
You're setting up a kind of cool motif of sound/silence (motifs are often opposite pairs)-- she hears, but she can't speak about it.