That's likely the case because they deliberately cloned his voice.
If you read the article, Google says they hired a professional voice actor to create the NotebookLM voice. I'm sure this will come to light in the lawsuit.
Doesn't seem like a very good clone. I wonder if he's hoping he's in their training data for a payout, if he can force that to be disclosed.
I think a few random samples trivially shows NotebookLM is higher pitched, although if you generalize to "deep male voice with vocal fry" you could lump them together with half the radio and podcast voices.
Unlikely. Most likely is that they used a lot of his podcasts in training and the AI picked a voice that was well represented in its training set because that's how it works.
Nobody at Google was like "we should use this guy's voice!"
I've been a pro sound engineer for 30 years, doing music, film, and producing podcasts for other people, plus I have years of prior training in elocution, which requires knowing about the anatomy and articulation dynamics of the human voice.
The voices don't sound that similar to me, and he has what I think of as a generic mid-atlantic accent. I'm sure it feels uncomfortably similar to him, but I think this is a mix of confirmation bias and the fact that radio and tv stations have long selected for 'average' sounding voices because listeners and viewers will call in to complain about voices they find annoying. Performers in this field cultivate those kind of generic voices, much as real estate agents cultivate aim for a friendly-but-bland look rather than trying to stand out individually.
I do feel for the guy a bit because voice generation is now so good that there's no reason to pay performers with a 'radio voice' for commercial voice-over or narration work in many cases, and I question the value of applying AI to fields of personal rather than industrial endeavor - was the cost of human vocalization such a drain on the economy that we are better off for automating those jobs away as quickly as possible? However, I don't buy his claim that his individual voice and way of speaking was stolen. It's just not very distinctive to me, in the same way that faces from thispersondoesnotexist.com will inevitably approximate the appearance of some real people.