1. A computer-implemented method comprising: obtaining audio samples of speech corresponding to a particular term; obtaining candidate pronunciations for the particular term; generating, for each candidate pronunciation for the particular term and audio sample of speech corresponding to the particular term, a score reflecting a level of similarity between the candidate pronunciation and the audio sample; aggregating the scores for each candidate pronunciation; and adding one or more candidate pronunciations for the particular term to a pronunciation lexicon based on the aggregated scores for the candidate pronunciations.