22. A computer-implemented method comprising: as implemented by one or more computing devices configured with specific computer-executable instructions, receiving, from a sensor configured to detect presence of a user independent of a direction of the user's gaze and without detecting physical contact between the user and the one or more computing devices, an indication that presence of the user was detected; begin listening for utterances from the user in response to receiving the indication; receiving a first voice signal corresponding to a first utterance of the user, wherein the first utterance is received by the one or more computing devices, and wherein the first utterance is not directed to the one or more computing devices; determining an identity of the user using the first voice signal; performing speech recognition on the first voice signal, using information from a user profile associated with the identity of the user, to obtain speech recognition results that indicate that a second utterance corresponding to a language characteristic is likely to be uttered by a second user different than the user at a time after a current time; performing an action using the speech recognition results; and selecting a second user acoustic model corresponding to the language characteristic for performing speech recognition.
22. A computer-implemented method comprising: as implemented by one or more computing devices configured with specific computer-executable instructions, receiving, from a sensor configured to detect presence of a user independent of a direction of the user's gaze and without detecting physical contact between the user and the one or more computing devices, an indication that presence of the user was detected; begin listening for utterances from the user in response to receiving the indication; receiving a first voice signal corresponding to a first utterance of the user, wherein the first utterance is received by the one or more computing devices, and wherein the first utterance is not directed to the one or more computing devices; determining an identity of the user using the first voice signal; performing speech recognition on the first voice signal, using information from a user profile associated with the identity of the user, to obtain speech recognition results that indicate that a second utterance corresponding to a language characteristic is likely to be uttered by a second user different than the user at a time after a current time; performing an action using the speech recognition results; and selecting a second user acoustic model corresponding to the language characteristic for performing speech recognition. 31. The method of claim 22 , wherein the information from the user profile was previously determined using speech recognition, and wherein the information comprises at least one of a name, hobbies, habits, or preferences of the user.