https://www.theverge.com/2017/8/18/16170672/sonos-smart-speaker-privacy-policy

Sonos plans to release new speakers with built-in microphones, likely with Alexa built in, and it wants to make sure you get every single hint. Its latest tease is an update to its privacy policy to cover voice assistants and microphones, which includes a not-so-subtle hint that voice-enabled Sonos products aren’t far off.

Voice control works by your voice-enabled Sonos Product “listening” for a specific wake word. Please note that not all Sonos Products are voice-enabled.