I doubt that using their customers' audio as training data was a major motivation for offering this service. But, assuming that was their plan, they'd have a c

I doubt that using their customers' audio as training data was a major motivation for offering this service. But, assuming that was their plan, they'd have a couple options: - Like you said, they could turn it into supervised training examples by transcribing it. I'm sure they'd at least like to transcribe some of it so that they can measure their performance. Also, while Google does have a lot of 1st party applications feeding them training data, customer data might help them fill in some gaps. - They might also be able get some value out of it without transcribing it. Neural networks can sometimes be pre-trained in an unsupervised manner. One example would be pre-training the network as an autoencoder, which just means training it to reproduce its input as its output. This can reduce convergence time.