Provide Captions and Transcripts
Both WCAG 2.0 guidelines and the Section 508 refresh (which incorporates by reference WCAG 2.0) require the use of captions for prerecorded synchronized media (basically, a video–audio combination) and transcripts for prerecorded audio. A learner with no hearing can get the content of a video only if captions are provided within that video and can get the content of an audio recording only if he or she can read a transcript.
Notably, captioning helps many users, regardless of disability. Captions can help students to focus, retain information, overcome poor audio quality, and more. In any case, captioning is a requirement when you provide video to your students.