I know many of our hens' vocalizations, too (and of course can tell the rooster crows apart).
Some are especially distinctive. Miss Eula makes a high-pitched, fingernails-on-chalkboard sound that doesn't match her big form. Bebe does a deep, "I'm planning your death" honk when she doesn't get her way.
I talk to the chickens as much as they talk to me, which is to say, a constant babble back and forth. I'm sure they know it's me by my voice but can't point to why.
Easier to prove that the roosters know bird voices, as they'll reply specifically to their hens and ignore calls from other groups.
Even when Andre's hens have flown over the fence and gone foraging on their own, 100' yards away and out of sight, when they bakaw in surprise at the greenhouse chipmunk, Andre immediately yells back from across the field while the other roosters ignore them.
Tax: coloratura soprano Eula and contralto Beebs.
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Glad to read I'm not the only one

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With the roosters, it's much easier; there are only three! The hens are a bit more difficult to tell apart, but I get by.
Kolovos has a "broken" crow. He crows, then it's a millisecond of very muffled sound, and then the crow continues. Big Red's crow doesn't stop in the middle, but I'd does end more abruptly.
I explain this to many different people, but they all look at me like I'm mad

. "Both crows sound the same, are you stupid?" Is very common.
Lady Gaga is obviously very easy to tell apart, given he is a tiny serama. When it comes to escort calls or normal vocalisations, Big Red's voice is very deep. Lady Gaga's is very high-pitched. Both boys are big chatters, talking almost all day. Big Red will not raise his voice, however. He always sounds very calm, even when he is in distress. Kolovos tends to be more expressive; he will not vocalise as much as the other two (probably due to how experienced he is, being so vocal while free ranging isn't always ideal) but he will typically raise his voice a lot more when he does vocalise.
When it comes to the hens, some I have not managed to "decode" yet. The pure brahma hens are almost silent, but when they do speak it's a very quiet "Honk".
The brahma mix pullet has inherited attributes from both parents; she will honk, but she is much more vocal and her honks are louder and more expressive. With this whole broody experience this summer I've gotten to know her very well, and apart from the boys, she is the one I can understand the most.
The Tsouloufati hens give me the most trouble. I can somewhat tell two to three apart.
The bantams are slightly easier. Ursula is also very big on talking. Back when she was not broody, she would squawk about every little thing she disliked. I put nesting material in the nests, squawk. I didn't put more food in her already full feeder, squawk. I was late to let the Tsouloufates out so she was burdened with having to watch them for longer, squawk. It soon became a game of me yelling "shut up!" and her responding with an even louder and longer-lasting squawk.
Cruella is a tough one. I've heard her voice once, when she saw a dead mouse in her pen the first few days of having her first brood. Other than that, only small "cluck clucks" when she's broody.
The serama hens are quiet too. I can only tell when Scary Spice is sounding escort or alarm calls, and that's because Lady Gaga will always respond to them; her voice is too quiet to hear otherwise
This probably makes me look a lot crazier, but it's fine. Chicken people weren't ever sane to begin with