audio the technology of sound reproduction Note Audio can be created synthetically (including speech synthesis), recorded from real
      world sounds, or both. audio description narration added to the soundtrack to describe important visual details that cannot
      be understood from the main soundtrack alone Note 1 Audio description of video provides information about actions, characters, scene changes, on-screen text, and
      other visual content. Note 2 In standard audio description, narration is added during existing pauses in dialogue.
      (See also extended audio description .) Note 3 Where all of the video information is already provided in existing audio , no additional audio description is necessary. Note 4 Also called "video description" and "descriptive narration." audio-only a time-based presentation that contains only audio (no video and no interaction) blinking switch back and forth between two visual states in a way that is meant to draw attention Note See also flash . It is possible for something to be large enough and blink brightly enough at the
      right frequency to be also classified as a flash.