15. A non-transitory computer-readable medium storing software comprising instructions executable by one or more computers which, upon such execution, cause the one or more computers to perform operations comprising: receiving an audio signal encoding a portion of an utterance; receiving context information associated with the utterance, wherein the context information is not derived from the audio signal or any other audio signal; generating, for input to a neural network of an automatic speech recognition system and based on characteristics of the context information that existed when the context information was received, characteristic data that corresponds to the context information; providing, as input to the neural network of the automatic speech recognition system, data corresponding to the audio signal and the characteristic data that corresponds to the context information; and generating a transcription for the utterance based on at least an output of the neural network.
15. A non-transitory computer-readable medium storing software comprising instructions executable by one or more computers which, upon such execution, cause the one or more computers to perform operations comprising: receiving an audio signal encoding a portion of an utterance; receiving context information associated with the utterance, wherein the context information is not derived from the audio signal or any other audio signal; generating, for input to a neural network of an automatic speech recognition system and based on characteristics of the context information that existed when the context information was received, characteristic data that corresponds to the context information; providing, as input to the neural network of the automatic speech recognition system, data corresponding to the audio signal and the characteristic data that corresponds to the context information; and generating a transcription for the utterance based on at least an output of the neural network. 16. The computer-readable medium of claim 15 , wherein providing, as an input to a neural network, data corresponding to the audio signal and the characteristic data that corresponds to the context information comprises providing, as an input to the neural network, a set of acoustic feature vectors derived from the audio signal.