Charles Napier was the second voice of the Incredible Hulk, taking over after Ted Cassidy died.
He is a well-known actor who also had a deep voice, which is what Kenneth Johnson was looking for when casting Cassidy's successor.
Not only did he voice the Hulk in the show (uncredited), He also voiced him in the three post-series movies (again, uncredited).
The Disciple[]
In this story, the Hulk's voice sounds like his, but it is never made clear. Bear in mind that Cassidy was still voicing the Hulk at this point and might have been unavailable for that episode. Listen closely and you will understand what I'm talking about.