The first essential component is the Audio Listener. This may sound familiar, as you had a warning at the start of the navigation section about having too many of these. The Audio Listener acts as a master switch to enable sound in a scene. As there should only be one Audio Listener in a scene, Unity automatically adds the component to any camera that is created. Because a scene must have at least one camera, this ensures that there will always be a listener. Remember to delete extra Audio Listeners when you create additional cameras.