You can always change it.
Settings / Language and input / Text-to-speech output
Under Google you can change the speed or select 1 of 6 languages
Under Samsung you can change the speed, select 1 of 8 languages, and 1 of 7 voice effects (normal, deep, robot, helium gas, etc.)
Just remember these setting are for any of the S3 Voice to text sounds. Driving directions under nav, driving mode announcements, etc. will use the same voice.