12. An audio device comprising: one or more processors; a plurality of microphones; an audio speaker configured to produce output audio; memory storing computer-executable instructions that, when executed by the one or more processors, cause the one or more processors to perform acts comprising: receiving, from the plurality of microphones, a plurality of audio signals representing input audio; generating, by the one or more processors for each of the plurality of audio signals, an indication indicating whether a corresponding audio signal contains a predefined expression; generating a parameter that indicates at least one of whether or not the output audio is currently being produced, whether or not the output audio contains speech, loudness of the output audio, or an echo characteristic of one or more of the plurality of audio signals; identifying, based at least in part on the indications, two or more audio signals, of the plurality of audio signals, that include the predefined expression; determining, based at least in part on the two or more audio signals and the parameter, that an occurrence of the predefined expression in the input audio is a result of an utterance of the predefined expression by a user; and in response to the determining, providing a wake notification corresponding to the predefined expression to the one or more processors to change a state of the audio device.
17. The one audio device of claim 12 , wherein the wake notification indicates a probability that the predefined expression has been uttered by the user.