I found this article interesting. I’ve been using the beta of iOS 11 and Siri definitely sounds more human. There are other nice tidbits about Siri in this article as well.
This fall, when iOS 11 hits millions of iPhones and iPads around the world, the new software will give Siri a new voice. It doesn’t include many new features or tell better jokes, but you’ll notice the difference. Siri now takes more pauses in sentences, elongates syllables right before a pause, and the speech lilts up and down as it speaks. The words sound more fluid and Siri speaks more languages, too. It’s nicer to listen to, and to talk to.