I was fortunate enough to work on the voice chrome when displayed on all of Amazon devices with a display. We filed the patent for Speech-based audio indicators (#10409552) back in September 2016. The customer invokes Alexa with the wake word “Alexa” or a corresponding physical or GUI button. This activates the voice chrome to show Alexa is listening. Voice chrome is a visual indicator of the Alexa attention states, such as Listening, Thinking, and Speaking. Most devices should use on-screen voice chrome, although you may use on-device LEDs to display the states instead.