To me, it sounded like Roger Waters's speaking voice, but I could be wrong.When it was originally recorded, a "normal voice" was used to trigger the vocoder. On the original mix the "normal voice " was mixed out and only the vocoder was heard.
In the new mix, the "normal voice " is now blended into the vocoder voice so you hear both.
Guthrie / Waters et al obviously decided that the vocoder voice by itself was a bit passé...hence the new mix.
The " normal voice " doesn't sound like anyone from PF ( to my ears anyway...I may be wrong ) so it could have been voice talent/ engineer/ roadie or whoever !