- (id) initWithURL: fileURL {
    NSLog (@"initializing a recorder object.");
    self = [super init];

    if (self != nil) {

        // Specify the recording format. Options are:
        //
        //      kAudioFormatLinearPCM
        //      kAudioFormatAppleLossless
        //      kAudioFormatAppleIMA4
        //      kAudioFormatiLBC
        //      kAudioFormatULaw
        //      kAudioFormatALaw
        //
        // When targeting the Simulator, SpeakHere uses linear PCM regardless of the format
        //  specified here. See the setupAudioFormat: method in this file.
        [self setupAudioFormat: kAudioFormatLinearPCM];

        OSStatus result =   AudioQueueNewInput (
                                &audioFormat,
                                recordingCallback,
                                self,                   // userData
                                NULL,                   // run loop
                                NULL,                   // run loop mode
                                0,                      // flags
                                &queueObject
                            );

        NSLog (@"Attempted to create new recording audio queue object. Result: %f", result);

        // get the recording format back from the audio queue's audio converter --
        //  the file may require a more specific stream description than was 
        //  necessary to create the encoder.
        UInt32 sizeOfRecordingFormatASBDStruct = sizeof (audioFormat);

        AudioQueueGetProperty (
            queueObject,
            kAudioQueueProperty_StreamDescription,  // this constant is only available in iPhone OS
            &audioFormat,
            &sizeOfRecordingFormatASBDStruct
        );

        ...
    }

    return self;
} 

// Configures the audio data format for recording
- (void) setupAudioFormat: (UInt32) formatID {

    // Obtains the hardware sample rate for use in the recording
    // audio format. Each time the audio route changes, the sample rate
    // needs to get updated.
    UInt32 propertySize = sizeof (self.hardwareSampleRate);

    AudioSessionGetProperty (
        kAudioSessionProperty_CurrentHardwareSampleRate,
        &propertySize,
        &hardwareSampleRate
    );

// When running in the Simulator, the kAudioSessionProperty_CurrentHardwareSampleRate
//  property is not available, so set it manually.
#if TARGET_IPHONE_SIMULATOR
        audioFormat.mSampleRate = 44100.0;
#warning *** Simulator mode: using 44.1 kHz sample rate.
#else
        audioFormat.mSampleRate = self.hardwareSampleRate;
#endif

    NSLog (@"Hardware sample rate = %f", self.audioFormat.mSampleRate);

    audioFormat.mFormatID           = formatID;
    audioFormat.mChannelsPerFrame   = 1;

    if (formatID == kAudioFormatLinearPCM) {

        audioFormat.mFormatFlags        = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
        audioFormat.mFramesPerPacket    = 1;
        audioFormat.mBitsPerChannel     = 16;
        audioFormat.mBytesPerPacket     = 2;
        audioFormat.mBytesPerFrame      = 2;
    }
}