SoundPool.cs

using UnityEngine;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using LiberiNet;

public class SoundPool : MonoBehaviour
{
    static SoundPool _instance;

    public GameObject SourcePrefab;

    List<PooledAudioSource> _freeSources;

    public static AudioSource Play (string clipId, float volume = 1f, float pitch = 1f)
    {
        return Play(clipId, Vector3.zero, volume, pitch);
    }

    public static AudioSource Play (AudioClip clip, float volume = 1f, float pitch = 1f)
    {
        return Play(clip, Vector3.zero, volume, pitch);
    }

    public static AudioSource Play (string clipId, Vector3 position, float volume = 1f, float pitch = 1f)
    {
        var clip = Resources.Load<AudioClip>(clipId);

        if (clip != null)
            return Play(clip, position, volume, pitch);

        return null;
    }

    public static AudioSource Play (AudioClip clip, Vector3 position, float volume = 1f, float pitch = 1f)
    {
        var source = _instance.GetFreeSource();

        if (source != null)
        {
            _instance._freeSources.Remove(source);

            source.transform.position = position;
            source.Target = null;
            source.Play(clip, volume, pitch);

            return source.audio;
        }

        return null;
    }

    public static AudioSource Play (string clipId, Component target, float volume = 1f, float pitch = 1f)
    {
        return Play(clipId, target.gameObject, volume, pitch);
    }

    public static AudioSource Play (AudioClip clip, Component target, float volume = 1f, float pitch = 1f)
    {
        return Play(clip, target.gameObject, volume, pitch);
    }

    public static AudioSource Play (string clipId, GameObject target, float volume = 1f, float pitch = 1f)
    {
        var clip = Resources.Load<AudioClip>(clipId);

        if (clip != null)
            return Play(clip, target, volume, pitch);

        return null;
    }

    public static AudioSource Play (AudioClip clip, GameObject target, float volume = 1f, float pitch = 1f)
    {
        if (target == null)
            return null;

        var source = _instance.GetFreeSource();

        if (source != null)
        {
            _instance._freeSources.Remove(source);

            source.Target = target.transform;
            source.Play(clip, volume, pitch);

            return source.audio;
        }

        return null;
    }

    private PooledAudioSource GetFreeSource ()
    {
        if (_freeSources.Count != 0)
            return _freeSources[0];

        var sourceGo = Instantiate(SourcePrefab) as GameObject;

        if (sourceGo != null)
        {
            sourceGo.name = SourcePrefab.name;
            sourceGo.transform.parent = transform;

            var source = sourceGo.GetComponent<PooledAudioSource>();
            source.SoundFinished += OnSoundFinished;

            _freeSources.Add(source);

            return source;
        }

        return null;
    }

    void OnSoundFinished (PooledAudioSource source)
    {
        if (!_freeSources.Contains(source))
            _freeSources.Add(source);
    }

    void Awake ()
    {
        if (_instance == null)
            _instance = this;

        _freeSources = new List<PooledAudioSource>();
    }

    void OnDestroy ()
    {
        if (_instance == this)
            _instance = null;
    }
}