https://arstechnica.com/tech-policy/2019/04/amazon-admits-that-employees-review-small-sample-of-alexa-audio/

Most of the time, when you talk to an Amazon Echo device, only Amazon's voice-recognition software is listening. But sometimes, Bloomberg reports, a copy of the audio is sent to a human reviewer at one of several Amazon offices around the world. The human listens to the audio clip, transcribes it, and adds annotations to help Amazon's algorithms get better.

“We take the security and privacy of our customers’ personal information seriously,” an Amazon spokesman said in a statement emailed to Bloomberg. “We only annotate an extremely small sample of Alexa voice recordings in order [to] improve the customer experience."