Randomizing Main Camera's audio source

I'm working on integrating audio to my game. I'm playing sound by attaching sound to camera's audio source.

But, I need to randomize the audio source of my camera. can some one please help me with this ?
how should I manipulate this ?

I'm currently using this:

Code (CSharp):

1. public class PlayRandomAudio : MonoBehaviour {
2.  
3.     public Camera MainCamera;
4.  
5.     public AudioClip[] sounds; // set the array size and fill the elements with the sounds
6.    
7.     void  PlayRandom ()
8.    
9.     { // call this function to play a random sound
10.         AudioSource.Instantiate(MainCamera);
11.         if (audio.isPlaying) return; // don't play a new sound while the last hasn't finished
12.         audio.clip  = sounds[(int)Random.Range(0.0f,4.0f)];
13.         MainCamera.audio.Play();
14.  
15.     }
16. }

 

I've not "done" audio... but what is this line

Code (csharp):

1.  
2. AudioSource.Instantiate(MainCamera);
3.  

meant to do? looks wrong...

 

That was part of trail on if this is the reason for not playing.
I achieved playing audio with this code.

Code (CSharp):

1. public class PlayRandomAudio : MonoBehaviour {
2.  
3.     public AudioClip[] sounds; // set the array size and fill the elements with the sounds
4.    
5.     void  Start ()
6.    
7.     {
8.         audio.clip  = sounds[(int)Random.Range(0.0f,4.0f)];
9.         audio.Play();
10.     }
11. }

But, on second level, the game becomes damn slow.
Any help here ?