AVAudioPlayer plays music in iPod 2nd gen and 3rd gen

Question

Hello everyone,

I'm trying to play an audio file in iPhone and iPod with AVAudioPlayer,
the code works fine in iPhone and iPod touch 4th generation, I could hear the music.
but when I test it on iPod touch 2nd, iPod touch 3rd, I couldn't hear anything.
Below is the code I use for playing audio file, is there anything I miss here:

NSString *zeroAudioPath = [[NSBundle mainBundle] pathForResource:@"TimerBell" ofType:@"aif"];
NSURL   *file = [[NSURL alloc] initFileURLWithPath:zeroAudioPath];
AVAudioPlayer *audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:file error:nil];
[file release];
self.zeroAudioPlayer = audioPlayer;
zeroAudioPlayer.delegate=self;
[audioPlayer release];
[zeroAudioPlayer prepareToPlay];
[zeroAudioPlayer play];

Thank you for reading!