使用AVAudioRecorder - 音频计量 - 结帐本教程 - 当用户吹入麦克风时取消 http://mobileorchard.com/tutorial-detecting-when-a-user-blows-into-the-mic/

Use AVAudioRecorder - Audio Metering - checkout out this tutorial - dettect when a user blows into mic http://mobileorchard.com/tutorial-detecting-when-a-user-blows-into-the-mic/

快速示例：

_audioRecorder.meteringEnabled = YES;

//1. This method will get the current mic activity and will format it to a 0 - 1 scale.

-(void)checkRecordingMeters:(NSTimer *)timer
{
      [_audioRecorder updateMeters];

      const double ALPHA = 0.2;
      float peakPower = [_audioRecorder peakPowerForChannel:0];

      double peakPowerForChannel = pow(10, (0.05 * peakPower));
      lowPassResults = ALPHA * peakPowerForChannel + (1.0 - ALPHA) * lowPassResults;

      NSLog(@"Meters: %f" , peakPower);
      NSLog(@"lowPassResults: %f \n" , lowPassResults);
}


//2. Call this method to run a loop timer to check the current mic activity
-(void)enableMettering:(BOOL)enable
{

    if(enable)
    {
        levelTimer = [[NSTimer scheduledTimerWithTimeInterval:0.03
                                                  target:self
                                                selector:@selector(checkRecordingMeters:)
                                                userInfo:nil
                                                 repeats:YES] retain];
    }
    else
    {
        [levelTimer invalidate];
        [levelTimer release];
    }
}