New Post: Audio Input Capturing from multiple devices

I'm using the NAudio library to capture Audio Input in C#:

int _deviceID;
double _previewVal;
private void PreviewData()
{
    WaveIn waveIn = new WaveIn();
    waveIn.DeviceNumber = _deviceID;
    waveIn.DataAvailable += waveIn_DataAvailable;
    int sampleRate = 8000; // 8 kHz
    int channels = 1; // mono
    waveIn.WaveFormat = new WaveFormat(sampleRate, channels);
    waveIn.StartRecording();
}
void waveIn_DataAvailable(object sender, WaveInEventArgs e)
{
    for (int index = 0; index < e.BytesRecorded; index += 2)
    {
        short sample = (short)((e.Buffer[index + 1] << 8) |
                                e.Buffer[index + 0]);
        _previewVal = sample / 327.68f;
    }
}

The function PreviewData is called simultaneously for each audio input device (which are 4 in my system). When I only call the method for one device it seems to be working but if I call it once more I get the exception "AlreadyAllocated calling waveInOpen". Does someone know how to work around this?