Unity Oneshot with Audiosource

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

public static class AudioClipExtention
{
    static List<PooledAudioSource> sourcesPool = new List<PooledAudioSource>();
    public static int totalNumberOfAudioSources;
    public static Transform parent;
    public static int maxSourcesCount = 32;

    public static void PlayWithSource(this AudioClip aClip, object caller)
    {
        PooledAudioSource p = ReturnSource();
        if (p == null) { Debug.LogWarning("Could not play the clip: " + aClip.name + " because there are more than " + maxSourcesCount + " sources in the scene."); return; }

        p.Play( caller, aClip);
    }

    public static void PlayWithSource(this AudioClip aClip, object caller, float volume, float pitch)
    {
        PooledAudioSource p = ReturnSource();
        if (p == null) { Debug.LogWarning("Could not play the clip: " + aClip.name + " because there are more than " + maxSourcesCount + " sources in the scene."); return; }

        p.Play(caller, aClip, volume, pitch);
    }

    public static void SourceFinishedPlaying(PooledAudioSource ps)
    {
        sourcesPool.Add(ps);
    }

    static PooledAudioSource ReturnSource()
    {

        if(sourcesPool.Count >0)
        {
            PooledAudioSource toReturn = sourcesPool[sourcesPool.Count - 1];
            sourcesPool.RemoveAt(sourcesPool.Count - 1);
                return toReturn;
        }

        if (totalNumberOfAudioSources >= maxSourcesCount) return null;

        return new PooledAudioSource();
    }
}

public class PooledAudioSource
{

    AudioSource source;

    public PooledAudioSource()
    {
        if(source == null)
        {
            source = new GameObject().AddComponent<AudioSource>();
            AudioClipExtention.totalNumberOfAudioSources++;
            source.gameObject.name = "Pooled_AudioSources_" + AudioClipExtention.totalNumberOfAudioSources;
            if (AudioClipExtention.parent == null) AudioClipExtention.parent = new GameObject("PooledAudios").transform;
            source.gameObject.transform.parent = AudioClipExtention.parent;

            source.playOnAwake = false;
            source.loop = false;
        }

    }

    public void Play(object caller, AudioClip c)
    {
        source.enabled = true;
        source.clip = c;
        source.Play();

        ((MonoBehaviour)caller).StartCoroutine(TrackProgress(c.length));
    }

    public void Play(object caller, AudioClip c, float volume, float pitch)
    {
        source.enabled = true;
        source.clip = c;
        source.volume = volume;
        source.pitch = pitch;

        source.Play();

        ((MonoBehaviour)caller).StartCoroutine(TrackProgress(c.length));
    }

    IEnumerator TrackProgress(float length)
    {
        yield return new WaitForSeconds(length+0.1f);
        FinishedPlaying();

    }
    void FinishedPlaying()
    {
        source.clip = null;
        source.enabled = false;
        AudioClipExtention.SourceFinishedPlaying(this);
    }

}