AVAudioPlayer  *player;
NSString       *path;
NSError        *error;
 
// Path the audio file
path = [[NSBundle mainBundle] pathForResource:@"sound-file" ofType:@"mp3"];
 
// If we can access the file...
if ([[NSFileManager defaultManager] fileExistsAtPath:path]) 
{    
  // Setup the player
  player = [[AVAudioPlayer alloc] initWithContentsOfURL:
     [NSURL fileURLWithPath:path] error:&error];
 
  // Set the volume (range is 0 to 1)
  player.volume = 0.4f;
 
  // To minimize lag time before start of output, preload buffers      
  [player prepareToPlay];
 
  // Play the sound once (set negative to loop)
  [player setNumberOfLoops:0];
 
  [player play];    
 
}    
 
...
 
// Cleanup
if (player != nil)
{
  if (player.isPlaying == YES)
    [player stop];
  [player release];
}