Web Accessibility in Mind (Web Aim): Captions, Transcripts and Audio Descriptions

Accessible multimedia should include captions so it is accessible to people who can't hear the audio well or at all. This also helps people who are still learning a language, when there is a lot of environmental noise, or where one must be quiet. Guidelines for good captioning are explained here. The article also discusses the use of transcripts and using audio descriptions of video for those who are unable to see.