How to stop Siri’s voice from reverting to robotic on iOS

“You’ll never appreciate just how good Siri’s voice is today unless you hit this problem where your iPhone sheds it in favor of the original 2011-era robotic sound,” William Gallagher writes for AppleInsider. “Once you’ve appreciated it, though, here’s how to put it right again.”
“Now that we’ve had several years of steadily improving audio from Siri, we’re now at a stage where it sounds practically natural. Or at least, it does when you compare it to the original —and you may find yourself doing exactly that,” Gallagher writes. “It’s not a very common problem, fortunately, but at times your iPhone will abruptly revert to that original voice. If it happens to you, it’ll probably be just before you set out on a long drive and Siri’s navigation instructions will irritate you at every single turn along the way.”
How to restore Siri’s voice, if it goes robotic here.
MacDailyNews Take: Apple’s considerable work on making Siri’s speaking voice sound more natural over the years is chronicled in the best-selling behind-the-scenes book Polishing a Turd.
Seriously, though, we expect Apple to reveal some substantial Siri improvements that make the tech not only sound better, but finally work better in a few months at WWDC 2019.