Sounds gets distorted when played

Hi folks,

in Unity3D when I try to play sounds of multiple explosions I get weird explosion-sounds, i.e. they sound distorted. I already tried to set the dopplerLevel to zero but that didn't do the trick. I do not get any bugs. Any help, please?

 //sets up an array of AudioClips and gets populated via Resources.Load
 AudioClip[] enemyExplSnds = new AudioClip[7];
         for (int i = 0; i < enemyExplSnds.Length; i++) {
             enemyExplSnds[i] = Resources.Load("Sound/explosions/enemies/explosion_" + i) as AudioClip;
         }

 //this plays random sounds
 int randomExplSndVal = Random.Range(0, enemyExplSnds.Length);
             SoundManager.PlaySFX(enemyExplSnds[randomExplSndVal]);

 //This is the method that plays the sound:
 public static void PlaySFX(AudioClip sfxClip) {
 //PlaySFX is the simplest, all we do here is get the SoundManager instance, fetch a new SFXSource and use it to play
 //the clip before stating the RemoveSFXSource coroutine to clean it up.
         SoundManager soundMan = GetInstance();
         AudioSource source = soundMan.GetSFXSource();
         source.volume = GetSFXVolume ();
         source.clip = sfxClip;
         source.loop = false;
         source.Play();
         soundMan.StartCoroutine(soundMan.RemoveSFXSource(source));
     }

 //This is the method GetSFXSource:
 AudioSource GetSFXSource() {
         // set up a new sfx sound source for each new sfx clip
         AudioSource sfxSource = gameObject.AddComponent<AudioSource>();
         sfxSource.loop = false;
         sfxSource.playOnAwake = false;
         sfxSource.volume = GetSFXVolume();
 
         if (sfxSources == null) {
             sfxSources = new List<AudioSource>();
         }
 
         sfxSources.Add(sfxSource);
         return sfxSource;
     }

 //This removes the sound:
 IEnumerator RemoveSFXSource(AudioSource sfxSource) {
         yield return new WaitForSeconds(sfxSource.clip.length);
         sfxSources.Remove(sfxSource);
         Destroy(sfxSource);
     }