You can set your Amazon Echo and Google Home or Nest devices to give you audio cues when they start and stop listening for commands.
Both Amazon’s and Google’s smart speakers (such as the Echo Dot and the Nest Mini) and smart displays (e.g., the Echo Show and the Nest Hub Max) always keep an ear out for the “Alexa” or “Hey Google” wake words respectively, but it’s only after you’ve summoned Alexa or Google Assistant that they’ll record and transmit your requests to the cloud.
By default, Alexa and Google Assistant stop listening as soon as they’ve fulfilled a command or answered a query, although you can also set them to keep listening for follow-up questions. If you’ve enabled the “Follow-up Mode” (for Alexa) or “Continued Conversation” setting (for Google Assistant), your device will keep listening for several more seconds in case you want to ask more questions or issue more voice commands.