Thanks for the quick response Caleb,
I am running it on a Win 10 machine through steam. After posting this I managed to find someone mentioning the location of the VO files and on inspection, it seemed a little lite on content. I have just started a new install and will get back to you with the log files if the problem exists.
After all the work those actors have put in there is no way I am playing this game without them whispering in my ear.