In this command, f=3200 sets the cut-off frequency to 3200 Hz. All frequencies above this will be filtered out.
But later comments about using a LADSPA plugin are less helpful
The exact steps can vary depending on your system configuration and the specific LADSPA plugin you choose to use.
PulseAudio documentation for module-ladspa-sink has a working example of how to implement a 10 band equalizer. But suggests using jack_rack in JACK to work out the settings for other LADSPA plugins
An equalizer could be used instead of a low pass filter by zeroing settings for lower frequencies and reducing high frequency bands only. pulseaudio-equalizer-ladspa has a GUI for setting up the same LADSPA multiband equalizer. the GUI can be used to set up the equalizer by ear and then configuration can be found in PulseAudio configuration ( grep ladspa ~/.config/pulse/default.pa )
that can be converted into terminal commands to load the module without installing GUI
For a lowpass filter that starts to rolloff frequencies at 10kHz and cuts everything above 20kHz:
The initial post is completely without context, so I would assume your crystal ball is a little cloudy.
I have good quality audio - and so rather than abusing the path from file to ears, 'd be thinking along the lines of inputting audio or video and outputting the same file with modified frequency response rather than modifying the processing of all audio…
So tweaking MPV, or using an equaliser to do that job is a great solution - modifying Pipewire or Pulseaudio to affect the entire system would be a brutal stroke, useful only if your audio equipment is inadequate…
OP doesn’t state where the filters need to be applied, or why… and has chosen a solution which is actually a long post specifying both methods. I guess we’ll never know… but I’ll throw you an upvote anyway for having such a coool name
The assumption that I can’t find the docs on my own feels insulting. And people searching for this question in the future and finding someone saying RTFM will be discouraged from opening links to this forum again if that’s the kind of answers they’ll find. Just imagine how many fewer people would use and contribute to forums like Stack Exchange if all answers were like that.
Post #4 is responding to questions in post #1 about PulseAudio and mpv
OP posted information about system and PulseAudio in other recent posts so further context is not needed
I do not consider modifying Pulseaudio is ‘brutal’ when any DSP can be bypassed in GUI controls
Other users do not need to know which solution OP preferred to try their own solutions
I would usually implement DSP in JACK but that is not relevant to this topic