Here I have an example.
Well I took an existing generator and add LowPassFilter & HighPassFilter for Pink Noise & WhiteNoise and duration
I did some test with an analyzer (SmaartLive). this example seems correct
I use as a reference the dll NAudio 1.6.
If you want a more powerful filter, you will have to use FFT.
And not enough time to make an example.
example is available in WeTranfert here ::
https://www.wetransfer.com/dl/N7a9W05a/dede49dd367271447614f812590cb0b1eb5b5db0d9fb2020662074973bd5768975ff26506369f74
Publisher Visual Studio Express 2012