I tried searching for things about HD, HD Voice, but I didn't find other threads, so I apologize if I'm beating a dead horse.
My girlfriend, her mother, and I all hate the way HD calling sounds. It's very...I dunno, robotic? and every time I see it's an HD call I'm just like, ugh. I'm very rarely in a situation where I care about the omission of background noise, so I don't see the benefit.
I know there's not a way to turn it off in the account, but what about on an individual device? We have S6's and a Moto X pure in the mix.