Low pass filter

Can the low pass filter or high pass filter have a setting higher then 48DB?

You could apply the filter multiple times.
(This is known as “cascading”).

If you apply a 12 dB per octave filter to the same sound twice, it is approximately the same as running a 24 dB per octave filter once, (though the transition from passband to stop band will be more gradual with multiple passes).

The free version of TDR Nova has up to 72dB high & low pass filters.
The 32-bit VST2 version of that plugin works in Audacity on Windows.

have a setting higher then 48DB?

Scientific application, or actual sound? We are warned that “brick wall” filters tend to not sound very good. That’s one of the reasons the Audacity built-in ones don’t go any higher than they do.

Natural musical sounds usually have a base tone and a bunch of harmonics and overtones.

That’s one single piano note, “G1” (49Hz) way over on the left of the keyboard. All the rest of those tones (measured along the bottom) are what make that piano sound like a piano. Some of those tones buck instead of add. If you take them away, tonal distortion may go up. Even worse, you’re taking sound away, but the volume of the note may go up.


If you need an extremely steep filter, use “Spectral Delete”: https://manual.audacityteam.org/man/spectral_delete.html

It’s possible there are a number of other tools to do what you want. For example the mains hum filter and frying mosquito USB microphone errors. Those are careful surgical deletions and sometimes you can’t tell they’re running.

Those are both “rescue” tools intended to turn an already recorded show with damage into a successful show, or at least one that’s not trash. In all cases it’s a good idea to fix the recording problem.