A single pole recursive lowpass filter for reducing high frequency audio content with 6 dB/octave. The filter frequency is expected to be normalized, ie. between 0 and 0.5. The normalized frequency is simply the target frequency divided by the sample rate (eg. 1000Hz / 44100Hz = 0.02267). To let the filter ring out, a number of samples can be specified that will be appended as zeros to the input, and extend the filter response by the same number of samples.
The input is not modified.