Help turning off one sound.

every thing works as I would like it to except for the hum. it does not turn off.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class LightSaber : MonoBehaviour
{
    public ParticleSystem particles;
    public GameObject redlight;
    public AudioClip ignition;
    public AudioClip hum;
    AudioSource audioSource;
    
    
    // Start is called before the first frame update
    void Awake()
    {
        particles = GetComponentInChildren<ParticleSystem>();
        audioSource = GetComponent<AudioSource>();
    }

    private void Start()
    {
        redlight.SetActive(false);  //turns light off at start
    }

    void Update()
    {
        if (Input.GetKeyDown(KeyCode.R))
        {
            var em = particles.emission; //emission needs to be off in the inspector.
            em.enabled = !em.enabled;  //this toggles it on.
            redlight.SetActive(!redlight.activeSelf); //this turns the light on and off
            audioSource.PlayOneShot(ignition, 0.7f); // sound plays each time you press R
            audioSource.PlayOneShot(hum, 0.2f); // this sound comes on but will not turn off.
        }
        
       
    }

}

From your code, it looks like it should work to me!
I don’t see why the ignition audio should behave any different from your hum audio. I did wonder if your audioSource was looped somehow, but then you would hear a looping ignition sound, which it doesn’t sound like you are.

The only thing I can maybe think is perhaps your hum audioclip is a really long sound clip?