An augmented reality (AR) device can be configured to monitor ambient audio data. The AR device can detect speech in the ambient audio data, convert the detected speech into text, or detect keywords such as rare words in the speech. When a rare word is detected, the AR device can retrieve auxiliary information (e.g., a definition) related to the rare word from a public or private source. The AR device can display the auxiliary information for a user to help the user better understand the speech. The AR device may perform translation of foreign speech, may display text (or the translation) of a speaker's speech to the user, or display statistical or other information associated with the speech.