1. A method implemented by a system of one or more computers, comprising: receiving, by the system of one or more computers, speech utterances encoded in audio data and a transcript having text that represents the speech utterances; extracting, by the system of one or more computers, prosodic contours from the utterances; extracting, by the system of one or more computers and from the transcript, attributes of text associated with the utterances; for pairs of utterances from the speech utterances, determining, by the system of one or more computers, distances between attributes of text associated with the pairs of utterances; for the pairs of utterances from the speech utterances, determining, by the system of one or more computers, distances between prosodic contours for the pairs of utterances; generating, by the system of one or more computers, a model based on the determined distances for the attributes and the prosodic contours, the model adapted to estimate a distance between a determined prosodic contour for a received utterance and a prosodic contour for a synthesized utterance when given a distance between an attribute of text associated with the received utterance and an attribute of text associated with the synthesized utterance; and storing, by the system of one or more computers, the model in a computer-readable memory device.