Footsteps via script

Hello,

I know this has been questioned many times as I've read majority of the posts regarding this, so I coded a footstep script in C# which works to some extent but the audio plays like crazy if you know what I mean? Example you walk on a certain texture on the terrain, it plays but very fast when walking but say you took a baby step at a time it plays fine which you would expect anyway. I have put a few checks in to stop it playing when the Rigidbody is sleeping or if the Character Controller is not grounded and vice versa.

Here's the script:

 using UnityEngine;
 using System.Collections;
 
 [RequireComponent(typeof(AudioSource))]
 
 public class FootstepManager : MonoBehaviour
 {
 
     private AudioSource m_Audio;
     public AudioClip[] _GrassSounds;
     public AudioClip[] _MudSounds;
     public AudioClip[] _GravelSounds;
     public CharacterController _CharController;
     private Rigidbody _RigBod;
     private bool playSteps;
 
     void Awake()
     {
         m_Audio = gameObject.AddComponent<AudioSource>();
         _RigBod = _CharController.GetComponent<Rigidbody>();
     }
 
     void Start()
     {
         StartCoroutine(PlayFootstep());
         playSteps = true;
     }
 
     void Update()
     {
         if (!_CharController.isGrounded && playSteps)
         {
             playSteps = false;
             StopCoroutine(PlayFootstep());
         }
         else if (_CharController.isGrounded && !playSteps && _CharController.velocity.magnitude > 0.2f)
         {
             StartCoroutine(PlayFootstep());
         }
     }
 
 
     IEnumerator PlayFootstep()
     {
         int curSplatIndex = TerrainSurface.GetMainTexture(transform.position);
 
             switch (curSplatIndex)
             {
                 case 0:
                    yield return new WaitForSeconds(0.4f);
                    m_Audio.PlayOneShot(_GrassSounds[Random.Range(0, _GrassSounds.Length - 1)]);                   
                    break;
                 case 1:
                     m_Audio.PlayOneShot(_GravelSounds[Random.Range(0, _GravelSounds.Length - 1)]);
                     break;
                 case 2:
                     m_Audio.PlayOneShot(_MudSounds[Random.Range(0, _MudSounds.Length - 1)]);
                     break;
             }
         }
 
     }
 

I have tried many ways of trying to solve this but to no 'avail, hopefully someone can point me in the right direction!

Thanks in advance!