Yet another Audio on Collision issue

Hi guys!

I'm sure you're all sick of seeing these issues here, but i'm stuck.

I've looked all through the relevant information, tried a handful of different approaches, all for bupkis.

So, please tell me what i've done wrong!

Effectively, i have a small floating cube (with a rigidbody and IsTrigger collider) which is collected when the Player's sphere passes through it (it's my take on the tutorial game). All the expected effects occur (score rewarded, new cube appears, message appears in Console) except the sound I'm trying to add.

Code as follows

 {
     public float tumble;
     public AudioClip ding;
     
     void Start ()
     {
         rigidbody.angularVelocity = Random.insideUnitSphere * tumble;
     }
 
     void OnTriggerEnter (Collider other)
     {
         if (other.tag !="Player")
         {
             Debug.Log ("Intersect_Not_Player");
             return;
         }
         Debug.Log ("DING!");
         audio.PlayOneShot(ding,1.0f);
     }
 }

(Ignore the first few lines, unrelated movement script applied to same object)

I get the DING! console message without a problem, and the sound is audible if i set it to Play On Awake, but will not play under any other circumstances. Most vexing.

I've tried with the sound in a public Audioclip, i've tried a Audio Source on the prefab, I've tried all the solutions i could find with C# (People seem to use Javascript around here a lot).. and i got nothing. Sound refuses to play when it's meant to.

Any ideas peeps?

Sam