Video.js how to add audio track without src parameter?

Question

JavaScript

var track = new videojs.AudioTrack({
  id: 'my-spanish-audio-track',
  kind: 'translation',
  label: 'Spanish',
  language: 'es'
});
player.audioTracks().addTrack(track);

Here, in general, an audio track type is added, but I don’t understand where it takes it from, since there is no src parameter there,
where does it take it from? And what is the right way to add it?
from example: docs.videojs.com/docs/guides/audio-tracks.html