Why not just rip the audio file off? Would make for a funny DC request
Edit: On second thought this could be an OPSEC problem. Sorry but I don’t know if anyone can help you :(
I bet the tts voice is public and something made by AT&T in the 80s or 90s.
If I were the president I would install this on random doors in the White House as a prank. It would be fun to watch the NSC fumble for their phone when walking into the oval.