Ok so I'm assuming literally almost everyone thought Ned was back for a hot second at the end of ep 29.
Imagine tho if that similarity in voice is actually a thing in-universe.
Maybe Aubrey doesn't notice it that first day, too excited by the magic working. But that adrenaline fades, and the realizations come in little moments.
Sometimes Thacker speaks somewhere across the room and her head snaps around because she knows that voice and she told him to leave but he didn't but he's still gone -
And sometimes she's speaking to the guy, and he'll say something and she keeps getting thrown off her rhythm because its never what she expects him to be saying.
And sometimes, the worst times, on sleepy mornings following sleepless nights, she'll be eating breakfast and barely think of anything at all, and Thacker talks to Barclay and she doesn't hear the words they're saying, just the rhythm and lilt of it all and for a few seconds she forgets the past couple of months have happened at all. Ned is here, and the town is fine, and Dani was never possessed and locked away who knows where for who knows how long, and then she looks up and remembers and it feels like losing everything all over again.
And when Thacker meets Duck. Aubrey sees the bewilderment on his face and knows he hears it too - it's not just her dwelling on ghosts.
(If only Ned had been a ghost. He would've gotten a kick out of that.)
She mentions it convincingly off-hand to Barclay, and he doesn't seem surprised, just sad and understanding. He and Mama went through the same thing when they first met Ned, apparently, long before Aubrey came to Kepler. And again when they first realized Thacker'd been gone a little too long on his research excursion. Barclay says it's something that will fade with time.
Aubrey hopes it does, and hopes they have that long. But until then, she tries her best not to let Thacker see the way hearing him talk chafes at the still raw exit wound Ned left behind. It's not his fault after all. But it's hard, because she keeps remembering the last words she said to Ned, and sightless eyes staring at stars above.