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 geotagged audio signals (130a-c) that correspond to environmental audio recorded in multiple geographic locations (132a-c); storing the geotagged audio signals in a data store; receiving an audio signal that corresponds to an utterance recorded by a particular mobile device, wherein the utterance represents a voice search query, or an input to a digital dictation application or a dialog system, and determining a particular geographic location associated with the particular mobile device; generating a noise model for the particular geographic location using a subset of the geotagged audio signals, wherein generating the noise model comprises determining, for each of the geotagged audio signals, a distance between the particular geographic location and a geographic location associated with the geotagged audio signal and selecting the subset of the geotagged audio signals for which the geographic locations associated with the geotagged audio signals are within a predetermined distance of the particular geographic location; and performing noise compensation on the audio signal that corresponds to the utterance using the noise model that has been generated for the particular geographic location. 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 geotagged audio signals (130a-c) that correspond to environmental audio recorded in multiple geographic locations (132a-c); storing the geotagged audio signals in a data store; receiving an audio signal that corresponds to an utterance recorded by a particular mobile device, wherein the utterance represents a voice search query, or an input to a digital dictation application or a dialog system, and determining a particular geographic location associated with the particular mobile device; generating a noise model for the particular geographic location using a subset of the geotagged audio signals, wherein generating the noise model comprises determining, for each of the geotagged audio signals, a distance between the particular geographic location and a geographic location associated with the geotagged audio signal and selecting the subset of the geotagged audio signals for which the geographic locations associated with the geotagged audio signals are within a predetermined distance of the particular geographic location; and performing noise compensation on the audio signal that corresponds to the utterance using the noise model that has been generated for the particular geographic location. receiving geotagged audio signals (130a-c) that correspond to environmental audio recorded in multiple geographic locations (132a-c); storing the geotagged audio signals in a data store; receiving an audio signal that corresponds to an utterance recorded by a particular mobile device, wherein the utterance represents a voice search query, or an input to a digital dictation application or a dialog system, and determining a particular geographic location associated with the particular mobile device; generating a noise model for the particular geographic location using a subset of the geotagged audio signals, wherein generating the noise model comprises determining, for each of the geotagged audio signals, a distance between the particular geographic location and a geographic location associated with the geotagged audio signal and selecting the subset of the geotagged audio signals for which the geographic locations associated with the geotagged audio signals are within a predetermined distance of the particular geographic location; and performing noise compensation on the audio signal that corresponds to the utterance using the noise model that has been generated for the particular geographic location.