AudioClip not showing up in inspector CSHARP

using UnityEngine;
using System.Collections;

public class player_controller : MonoBehaviour {
	AudioClip sound;


The above is a simplified version of my code. (by that I mean I cut everything else out)
The problem that i’m having is that when I go back into the inspector (after saving in monodevelop) there ISNT this:

Im talking about the part that says sound and has the box you can drag audio into. Mine doesn’t have that.
I think that I am doing something obviously wrong but I just cant see it. Thanks in advance for any help I get.

Inspector only shows fields for variables that can be serialized. Public variables are serialized by default.

 public AudioClip sound;

You can also expose private variables with the SerializeField attribute.

private AudioClip sound;

If you do not specify public or private, then the member is private by default in classes.