One of the videos had somebody with a non-US accent -- British, maybe? Can't see...

greyish_water · on Oct 12, 2011

http://www.stuff.tv/video/vidcasts/apple-iphone-4s-siri-demo

Also worth noting that evidently Siri's voice can be changed, as well. That was a safe bet, but I hadn't seen it mentioned anywhere.

ugh · on Oct 12, 2011

The voice seems to depend on the language. You seemingly can't explicitly switch it, you only can switch languages. It just so happens that iOS has both 'English' and 'British English' as languages, with female and male voice synthesis respectivly. (Those languages are already built into the current version of iOS as part of VoiceOver.)

If you are German or French you only ever get one voice.