Playing sound through pickup trigger

Hey guys, I'm a bit confused to why my sound is not playing when I go through an object

using UnityEngine;

using System.Collections;

 public class Jewels : MonoBehaviour 
 
 {
     public GUIText jewelsText;
     public GUIText winText;
     public AudioClip Pickup;
     private int jewels;
     
 
 
     // Use this for initialization
     void Start () 
     {
         jewels = 0;
         SetJewelsText();
         winText.text = "";
     }
 
     void OnTriggerEnter(Collider other)
     {
         if(other.gameObject.tag == "Pickups")
         {
             other.gameObject.SetActive(false);
             jewels = jewels + 1;
             SetJewelsText();
         }
         if (Pickup)
         {
             audio.clip = Pickup;
             audio.Play();
         }
 
     }
     
     void SetJewelsText()
     {
         jewelsText.text = "jewels:" + jewels.ToString();
         if(jewels >=20)
         {
             winText.text = "You Collected all the jewels!";
         }
     }
     
 }