1. A method for constructing an expanded search query at a computing device, the method comprising: receiving audio information via a microphone of the computing device; recording the audio information in an overwriteable circular buffer of the computing device, including recording at least some of the audio information during a period when the computing device is powered-on, but is in an inactive state or a sleep state in which a graphical display of the computing device is off or substantially dimmed, said recording initiated responsive to a triggering condition including detection of a sound level via the microphone that exceeds a sound level threshold, the overwriteable circular buffer having a limited data storage capacity in which older audio information is overwritten with newer audio information upon reaching the limited data storage capacity; initiating construction of a search query by receiving a user input via a text-based user interface of the computing device, the user input including one or more keywords forming a user-defined portion of the search query; processing at least a portion of the audio information recorded in the overwriteable circular buffer to obtain one or more additional keywords forming an expanded portion of the search query, the portion of the audio information containing the one or more additional keywords received and recorded in the overwriteable circular buffer prior to receiving the user input including the one or more keywords; supplying the search query including the user-defined portion and the expanded portion to a search engine; and receiving a response to the search query from the search engine, the response generated by the search engine based, at least in part, on the one or more keywords of the user-defined portion and the one or more additional keywords of the expanded portion of the search query.