Problem with audio

I have a GameObject to which I attached an Audio Source Component. In the script attached to the GameObject I wanted to add the following lines:

 public AudioClip[] sound;
 
 public void play_sound(int n){
    audio.clip = sound[n];
    audio.Play()
 }

So whenever I want to play a sound I just call the play_sound function. Problem is that audio is not seen in the function for some reason. Why is this happening?