Not speaking for Alexa or Amazon, where I have worked in the past, but the wakeword detection is done separately in a much lower power, localized model using ha

Not speaking for Alexa or Amazon, where I have worked in the past, but the wakeword detection is done separately in a much lower power, localized model using hardware features. On the downside this means that you can only select from a few wakewords and the filtering etc. are limited (e.g. the local model is not aware of commercials being played concurrently in the world, so has to wake up the bigger model, which can check to see if that's happening). On the positive side, it's much lower power and mitigates concerns that Alexa is listening to normal activity/conversations.