How do they ‘detect’ the activation word without listening? Seems to me that is tautologically impossible. The definition of detect and listen are identical here. How do you detect sound waves without listening to them?
"Echo devices use on-device keyword spotting designed to detect when a customer says the wake word. This technology inspects acoustic patterns in the room to detect when the wake word has been spoken using a short, on-device buffer that is continuously overwritten. This on-device buffer exists in temporary memory (RAM); audio is not recorded to any on-device storage. The device does not stream audio to the cloud until the wake word is detected or the action button on the device is pressed. If it does not detect the wake word or if the action button is not pressed, no audio is sent to the cloud."
https://d1.awsstatic.com/product-marketing/A4B/White%20Paper...