4. The method of claim 3 wherein obtaining, by the first user device from the second user device used by the second user, a second speaker model that is specific to the second user comprises: generating, by the first user device, a second score that indicates a respective likelihood that the utterance was spoken by the second user using a portion of the audio signal and the second speaker model.
5. The method of claim 4 comprising: comparing the first score with the second score to determine a highest score, wherein determining that the utterance was spoken by the first user comprises determining that the first score is the highest score.