Resolved How might I trigger an audio oneshot when y position is <0 to play just once?

Expectation - When a ball rolls off the floor I want to trigger an audio oneshot to play a "falling" sound.
Problem - With this code the one shot plays many instances of the falling sound. I believe this is because the update continues to see this position as being < 0 and plays multiple instances of the audio file as long as y position is < 0.

Code (CSharp):

1. using UnityEngine;
2.  
3. public class Ball : MonoBehaviour
4. {
5.     public AudioClip ballFall;
6.     private AudioSource audioSource;
7.  
8.     void Start()
9.     {
10.         audioSource = GetComponent<AudioSource>();
11.     }
12.  
13.     void Update()
14.     {
15.         if (transform.position.y < 0)
16.         {
17.             audioSource.PlayOneShot(ballFall);
18.         }
19.     }
20. }

---
Does anyone have suggestions on how might I rewrite the code so the audio will play only once when the threshold is crossed and not again? Thanks!

 

This is working using a bool to tell if the clip was played resulting in a single play of the audio clip:

Code (CSharp):

1. using UnityEngine;
2.  
3. public class Ball : MonoBehaviour
4. {
5.     public AudioClip ballFall;
6.     private AudioSource audioSource;
7.     private bool clipPlayed = false;
8.     private float fallDelay = 0;
9.  
10.     void Start()
11.     {
12.         audioSource = GetComponent<AudioSource>();
13.     }
14.  
15.     void Update()
16.     {
17.         if (transform.position.y < fallDelay && !clipPlayed)
18.         {
19.             audioSource.PlayOneShot(ballFall);
20.             clipPlayed = true;
21.         }
22.     }
23. }