Я нашел решение по этой проблеме
Я использовал метод peakPowerForChannel и averagePowerForChannel AVAudioPlayer для получения децибел
AVAudioPlayer *avPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:recordedTmpFile error:&error];
avPlayer.delegate = self;
avPlayer.meteringEnabled = YES;
[avPlayer prepareToPlay];
[avPlayer play];
NSTimer *levelTimer = [NSTimer scheduledTimerWithTimeInterval: 0.03 target: self selector: @selector(levelTimerCallback:) userInfo: nil repeats: YES];
Этот метод возвращает пиковый пикPowerForChannel и averagePowerForChannel
- (void)levelTimerCallback:(NSTimer *)timer {
[avPlayer updateMeters];
NSLog(@"Peak left: %f Avg right: %f", [avPlayer peakPowerForChannel:0],[avPlayer averagePowerForChannel:0]);
}