Change this line:
NSURL *audioURL = [NSURL URLWithString:fileName];
to this:
NSURL *audioURL = [NSURL fileURLWithPath:fileName isDirectory:NO];
And then just do:
if(_audioPlayer == nil)
{
_audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:audioURL error:nil];
}
else
{
_audioPlayer = [self.audioAlert initWithContentsOfURL:audioURL error:nil];
}