https://www.theverge.com/2017/10/4/16418092/sonos-speaker-amazon-alexa-support-voice-assistant

Sonos announced today that its Alexa support, which has been in a limited private beta for months at this point, is finally rolling out to all current-model Sonos speakers in a public beta. The company’s latest speaker, the Sonos One, has a microphone built in, so you can just speak to it the way you would an Echo device.

Older Sonos speakers don’t have their own microphones, so Alexa integration is done through a connected Amazon Echo, Echo Dot, or any other Alexa device. A user would tell Alexa, “play music on my bedroom speaker,” and the audio would come from your Sonos device. A Sonos firmware update will be available shortly to enable Alexa on older units.