1. A method of buffering audio on an electronic device, comprising: detecting, at a first time, a first indication of impending device activity, the indicator comprising one or more of an activation of an application that processes audio, a change in incident light intensity, a visual recognition of motion, a visual recognition of a user in proximity to the electronic device, visual recognition of a face, a finger proximal to a touch-sensitive display screen, movement of the electronic device, ambient sound, speech, or recognition of a particular speaker; receiving, starting at a second time after the first time, audio corresponding to an utterance; storing audio data corresponding to the audio in a circular buffer, based at least in part on detecting the first indication; receiving, at a third time after the second time, a second indication to process audio; and in response to receiving the second indication: combining, into combined audio data, at least a portion of the audio data corresponding to the utterance and stored in the circular buffer prior to receiving the second indication with further audio data corresponding to further audio received after receiving the second indication; and sending the combined audio data for processing.