Kein Sound

public final class SoundManager implements IDisposeable
{
    private static SoundManager instance;
    
    private final int MAX_VOICES = 5;
    private SoundPool soundPool;
    private AudioManager audioManager;
    private ArrayList<SoundData> soundList;
    private int amount = 0;
    
    public SoundManager()
    {
        initialize();
    }
    
    private void initialize()
    {
        soundList = new ArrayList<SoundData>();
        
        soundPool = new SoundPool(MAX_VOICES, AudioManager.STREAM_MUSIC, 0);
        
        audioManager = (AudioManager)GameDriver.getInstance().getSystemService(Context.AUDIO_SERVICE);
        GameDriver.getInstance().setVolumeControlStream(AudioManager.STREAM_MUSIC);

    }
    
    public static SoundManager i()
    {
        if (instance == null)
        {
            instance = new SoundManager();
            Log.d("Status", "** instance created successfully!");
        }
        else
        {
            Log.d("Status", "** instance has already been created!");
        }
        
        return instance;
    }
    
    public void addSound(String path, String name, float volume)
    {
        try
        {
            AssetFileDescriptor descriptor = GameDriver.getInstance().getAssets().openFd( path );
            soundList.add(new SoundData(soundPool.load( descriptor, 1 ), name, volume));
            amount++;
        }
        catch( Exception ex )
        {
            Log.d( "Sound Sample", "** couldn't load sound '" + name + "'" );
            throw new RuntimeException( ex );
        }
    }
    
    public SoundData getSoundData(String name)
    {
        for (int i = 0; i < amount; i++)
        {
            if (soundList.get(i).ID_String == name)
                return soundList.get(i);
        }
        Log.e("Error", "'" + name + "' does not exist!");
        return null;
    }
    
    public void playSound(String name, int loop)
    {
        SoundData data = getSoundData(name);
        Log.d("Status" , "ID: " + data.ID_Num + ", " + data.ID_String);
        int volume = audioManager.getStreamVolume( AudioManager.STREAM_MUSIC ); // * data.volume;
        soundPool.play(data.ID_Num, volume, volume, 1, 0, 1);
    }
    
    public void dispose()
    {
        
    }
}

public class SoundData 
{
    public int ID_Num;
    public String ID_String;
    public float volume;
    
    public SoundData(int ID_Num, String ID_String, float volume)
    {
        this.ID_Num = ID_Num;
        this.ID_String = ID_String;
        this.volume = volume;
    }
}

SoundManager.i().addSound("sounds/synth_01.mp3", "synth", 1.0f);

// nach einer Wartezeit von ca 2 Sekunden dann...
SoundManager.i().playSound("synth", 2);