what is the source of google's pronunciations?

i've always held the cambridge learner dictionary's ones in high esteem.

e.g. https://dictionary.cambridge.org/dictionary/english/pronunci...

so many of the pronunciations I find on the web are just raw text-to-speech outputs that assume a generic pronunciation and fail for many words, in particular for names. I hope that the Google ones are actually human generated and verified, but am not confident of that.