[[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryRecord error:nil];
[[AVAudioSession sharedInstance] setActive:YES error:nil];

MCAudioInputQueue *_recorder;

AudioStreamBasicDescription format;
format.mFormatID = kAudioFormatLinearPCM;
format.mFormatFlags = kLinearPCMFormatFlagIsSignedInteger | kLinearPCMFormatFlagIsPacked;
format.mBitsPerChannel = 16;
format.mChannelsPerFrame = 1;
format.mBytesPerPacket = _format.mBytesPerFrame = (_format.mBitsPerChannel / 8) * format.mChannelsPerFrame;
format.mFramesPerPacket = 1;
format.mSampleRate = 8000.0f;

_recorder = [MCAudioInputQueue inputQueueWithFormat:format bufferDuration:0.2 delegate:self];
[_recorder start];

- (void)inputQueue:(MCAudioInputQueue *)inputQueue inputData:(NSData *)data numberOfPackets:(UInt32)numberOfPackets
{
    //handle data
}

- (void)inputQueue:(MCAudioInputQueue *)inputQueue errorOccur:(NSError *)error
{
    //handle error
}