"Object reference not set to an instance of an object" error

First and foremost here are the 2 scripts that i'm trying to make interact: Disregard variable initialization and "ThrowObject" method in the second script. Just there to add some context.

FIRST:

 using UnityEngine;
 using System.Collections;
 
 public class playerSounds : MonoBehaviour {
     
     public AudioClip step;
     public AudioClip punch;
     public AudioClip collision;
     public AudioClip fire;
 
     void Start () {
     
     }

     void Update () {
 
     }
     
     public void PlayClip(AudioClip clip){
     
     audio.clip = clip;
     audio.Play();
         
     }
 }

SECOND:

 using UnityEngine;
 using System.Collections;

 public class shootCrate : MonoBehaviour {
 
     public GameObject projectile;
     public GameObject referenceObj;
     public float addForceX = 0;
     public float addForceY = 250;
     public float addForceZ = 750;
     public float fireRate = 0.5F;
     public float nextFire = 0.0F;
     public float fireUp = 3; // spawn point distance up from the head
     public float dist = 2; // spawn point distance from the turret
     

     void Start () {
 
     }
 

     void Update () {
         playerSounds pSounds = GetComponent<playerSounds>();
         
         if ( Input.GetButton("Fire1") && Time.time > nextFire)
         {
             // Debug.Log("A key or mouse click has been detected");
             nextFire = Time.time + fireRate;
             ThrowObject();
             pSounds.PlayClip(pSounds.fire);
             
         }
     }
     
     
      void ThrowObject () {
             Vector3 projPos;
             projPos = new Vector3( transform.position.x,transform.position.y, transform.position.z  );
             projPos.y += fireUp;
             GameObject crateClone = Instantiate(projectile, projPos, referenceObj.transform.rotation) as GameObject;
             // Debug.Log("projectile created <"+projRot+">");           
             crateClone.rigidbody.useGravity = true;
     }
   
 }
 

So, when i actually try to run this i get the error mentioned in the title, that points to line 33 of the second method, which is the "pSounds.PlayClip(pSounds.fire);" bit in the Update(). Any ideas to why this is happening?

Thanks in advance.

Pedro