9. The system of claim 1 , wherein adapting one or more acoustic models for the geographic location type further comprises: selecting, from among multiple acoustic models that have been generated for multiple geographic location types, the one or more acoustic models generated for the geographic location type associated with the geographic location of the mobile device.
1. A system comprising: one or more computers; and a computer-readable medium coupled to the one or more computers having instructions stored thereon which, when executed by the one or more computers, cause the one or more computers to perform operations comprising: receiving an audio signal that corresponds to an utterance recorded by a mobile device, determining a geographic location associated with the mobile device, determining a geographic location type associated with the geographic location, selecting a subset of geotagged audio signals based on the geographic location type associated with the geographic location of the mobile device, and based on context data associated with the utterance, wherein the context data comprises data that references a time or a date when the utterance was recorded by the mobile device, data that references a speed or an amount of motion measured by the mobile device when the utterance was recorded, data that references settings of the mobile device or data that references a type of the mobile device; adapting one or more acoustic models for the geographic location type, and performing speech recognition on the audio signal using the one or more acoustic models that are adapted for the geographic location type.