To filter out high-pitched sounds on Linux using PulseAudio, you can use a low-pass filter. A low-pass filter allows sounds below a certain frequency to pass through while filtering out higher frequencies.

For MPV, you can apply a low-pass filter directly when playing a media file. The command would look like this:

mpv --af=lowpass=f=3200 yourfile.mp4

In this command, f=3200 sets the cut-off frequency to 3200 Hz. All frequencies above this will be filtered out.

For a system-wide solution, you can configure PulseAudio to apply a LADSPA low-pass filter to all audio. This process is more complex and involves installing and configuring the LADSPA plugin. The exact steps can vary depending on your system configuration and the specific LADSPA plugin you choose to use.

Another option is to use PulseEffects, a powerful real-time audio processing tool that works with PulseAudio. PulseEffects allows you to apply a variety of filters and effects to your audio, including a low-pass filter. You can adjust the cut-off frequency of the filter to target the high-pitched sounds you want to filter out.

Remember that filtering out high frequencies can affect the overall sound quality, potentially making it sound muffled or dull. You may need to experiment with different cut-off frequencies to find a balance that works for you.