I want to filter high pitched sounds in real time on Linux. So for example when watching a movie, if there is a big old TV or something and it has a high frequency sound that makes the ears ring, I would like to filter only those high frequencies if possible.
What you want is technically called a low-pass filter.
You can tell MPV (arguably the most efficient and best quality media player for linux) to apply a low-pass filter like this:
mpv --af=lowpass=f=3200 Titanic.mp4
Alternatively you can configure Pulseaudio (an audio layer coomonly used on linux desktops) to apply a LADSPA low-pass filter to all audio. This is described in detail here for Debian-based systems.
This is good enough, although I was thinking of something system wide.– user79017Mar 3, 2022 at 13:01
I suggest you update the question to clarify that you prefer system-wide solutions. Also helpful if you mention more detailed what you mean by "system-wide" - i.e. do your perception of "system" include all access to audio then you will prefer a filter for ALSA, if only common desktop-oriented access to audio then Pulseaudio filtering is more suitable - or perhaps you will be interest in modern desktop audio via Pipewire...– JonasMar 4, 2022 at 10:52