The Collaborative International Dictionary of English v.0.48:

audio \audio\ n.
   the part of a transmitted signal which conveys the sound of
   the event represented by the signal, such as that of a
   television program. "they always raise the audio for
   commercials"

   Syn: sound.
        [WordNet 1.5]

   2. 1 an audible acoustic wave frequency.

   Syn: audio frequency
        [WordNet 1.5]

   3. the sound elements of television.
      [WordNet 1.5]

WordNet (r) 3.0 (2006):

audio
    n 1: the audible part of a transmitted signal; "they always
         raise the audio for commercials" [syn: audio, sound]
    2: an audible acoustic wave frequency [syn: audio, audio
       frequency]
    3: a recording of acoustic signals [syn: sound recording,
       audio recording, audio]
    4: the sound elements of television

The Free On-line Dictionary of Computing (30 December 2018):

audio

    Sound, one component of multimedia.  Computers
   (and audio compact discs and digital audio tape) work with
   digital audio, in contrast to vinyl disks or analogue tape.

   (1999-07-30)