Spectral removal

Now I have a problem. I have seen from spectrogram view and spectrum analysis that pure tones below -x dB are waste which must be removed. Ok, I have tried Audacity but I haven’t found any tool which cleans up whole track and removes pure tones below wanted threshold. The signal is continuous, from machine hall, and I want to separate pump from another sounds and remove hum. Any ideas about plugin/another free program/trick how to do that?

High Pass filter: http://manual.audacityteam.org/o/man/high_pass_filter.html
For the steepest cut-off, set “Rolloff (dB per octave)” to 48.

As I understand it, he wants to eliminate sounds below a certain dB value, not a certain Frequency.
This suggests using the noise reduction with white noise–at the right dB level–as profile.
However, hum is another thing and should be treated with e.g. the notch filter.
There are also the spectral edit effects available…

You could well be right Robert. I read it as sounds below a certain frequency, as he specified “I have seen from spectrogram view and spectrum analysis”, and the subject of the post “Spectral removal”.
I’ve no idea what cryogenic means by “are waste which must be removed”.

cryogenic: Perhaps you could clarify what you mean, what you are trying to do (what’s the job? Why is this necessary and/or desirable? How will this help you to separate " pump from another sounds"?) .

Maybe this helps a little bit? This is an old hydropowerplant from 1920’s with original unit and there is an original technology in use, i.e. without signitificant revision/refurbishment. I’m creating simulator and this is one part of huge project.

At the picture is one part of a long track. We can see that there is white and red colors and these are wanted sounds. At the left and right side a hydraulic pump is feeding a governor system and creates pressure. At the middle, behind the vertical line, we can see blue “hole” which contains waste signals. At this time, pump creates flow without pressure. Some kind of valvesystem opens free circulation for oil to save energy. At the same time sound of pump stops. I think that it’s nice if I can remove most of hum/noise (in fact, useful signal is also in this category) and separate the sound of pump from basic sound of power plant unit. When the unit is increasing or decreasing power, it’s natural that governor makes work, needs oil and pump works longer periods. When unit works at the stable power, pump works only so much that inner leaks and fine filter(s) need.

If we think about sound, filtering sounds above 11-12kHz is one useful trick but same time it doesn’t need.
Pumppu seis.png

There’s a free VST plugin called DTBLKFX [ Windows & Mac, not Linux ] which has a “contrast” effect , which does that : increasing the contrast of the spectrogram …
Engine noise , before-after DTBLKFX contast +25%.png