Accessing low passed filtered audio data

Hi,

I am accessing data from a microphone via Audio.clip = Microphone.Start(null, true, 10, 44100);.

I would like to add a low pass filter and analyze the data hereafter. So, I have created a new Group in my AudioMixer, which includes the 'Lowpass Simple' Filter.

The Output of the Audio Source of my Object is set to the Lowpass group and the Audio Clip clip is a sample which contains a 440 Hz sine wave.

My expectation is that a cutoff frequency of 200 Hz would filter my 440 Hz file completely. However, I have to set the cutoff freq to 15Hz until I do not hear any tone anymore. Is this behavior perfectly fine or did I miss something?

Additionally, I would like to access the filtered data afterwards to analyze the spectrum. But the Lowpass filter does not seem to have any effect to GetOutputData and GeSpectrumData. Is the filter applied after the execution of my Script?

Do you prefer any other ways to filter audio data?

Thank you!