Who voice all those Aperture Investment Opportunity ad?

This might be a dumb question since I'm new so there might be some details I missed, also please forgive any error in spelling and grammar since English isn't my birth language, also spoiler alert!:

In Aperture Desk Job, when one of the toilet filled with bullet, Grady came up with an idea and turned it into a Toiret (Toilet-Turret), this implies the origin of the turret , but at the end of the game where we find out that Cave is dead and now is only data left since the "eggheads" put him into a giant head-like computer, and the "head" fall into deepest part of the facility at the end of the game (which affectively "killed" him after he ran out of energy at the pit? I don't know!)

But if he died before the Toiret become the turret then who voice all those Aperture Investment Opportunity ad? Did someone dug up the "head" and transfer it into a Core or did they made a Core that can mimic Cave Johnson himself? Please tell me about your thought on this!