It could any one of the English alternative voices (Australia, Scottish, Indian, Irish, etc), but it could also be a foreign voice speaking English.
For example, you can make the Mexican Spanish speak English - though he sounds like Ricky Ricardo the choice is there.
FWIW you can add voices if you have the HD space: System Preferences>Dictation & Speech>Text to Speech, click on System Voice, click to add Voice of choice ( you will need to download additional files - some are over 2 GB for ONE voice)