Amazon employs thousands of people to listen to voice recordings captured by Echo speakers in an effort to improve the software, according to Bloomberg.

The process: The Alexa voice review team includes both contractors and full-time Amazon staff working in offices around the world, including Boston, India, Romania, and Costa Rica. Each reviewer is expected to check about 1,000 audio files in each shift, two of the workers told Bloomberg. The recordings are transcribed, annotated, and fed back in hopes of improving Alexa, the software that powers Echo devices.

Privacy invasion: Sometimes the reviewers come across clips they find upsetting, or even potentially criminal. Amazon’s spokesperson responded thus: "We only annotate an extremely small sample of Alexa voice recordings in order [to] improve the customer experience."

Users can opt out of having their recordings used for development purposes, but Amazon doesn’t explicitly tell Echo customers that humans might be listening to them.

Controversy: While over 100 million people around the world own Alexa devices, many people choose not to, because they fear exactly this scenario: that Amazon could be listening in. This revelation today at least partly confirms the validity of their concerns.

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