1. A computer-implemented method comprising: receiving, by one or more computers, audio data corresponding to an utterance; generating, by the one or more computers, frequency domain data using the audio data; processing, by the one or more computers, the frequency domain data using complex linear projection; providing, by the one or more computers, the processed frequency domain data to a neural network trained as an acoustic model; and generating, by the one or more computers, a transcription for the utterance that is determined based at least on output that the neural network provides in response to receiving the processed frequency domain data.