public static void MixStereoToMono()
        {
            byte[] input = File.ReadAllBytes("options.wav");
            byte[] output = new byte[input.Length / 2];
            int outputIndex = 0;
            for (int n = 0; n < input.Length; n += 4)
            {
                int leftChannel = BitConverter.ToInt16(input, n);
                int rightChannel = BitConverter.ToInt16(input, n + 2);
                int mixed = (leftChannel + rightChannel) / 2;
                byte[] outSample = BitConverter.GetBytes((short)mixed);

                // copy in the first 16 bit sample
                output[outputIndex++] = outSample[0];
                output[outputIndex++] = outSample[1];
            }
            File.WriteAllBytes("options1.wav", output);
        }