Susan Bennett, of Greater Atlanta.
https://www.youtube.com/watch?v=z2bTymnb1uE
Apple broke her voice into syllables. When the Siri-bot needs to say something, Apple's software stitches the appropriate syllables together and speaks them.
It depends now on which voice you choose and also the language. There are multiple Siris. Austrailian male, Brit male, Japanese, Chinese, French woman, Russian woman, etc. Apple has been busy exptending Siri.
Apple was building on the tradition of Jane Barbe and Pat Fleet (those all too familiar “telephone voices”):
http://www.beatriceco.com/bti/porticus/bell/recordedannouncements.html