When sound is above 0.9 I would like randomly cut that amplitude and some part I would like to make it like a sine curve.
So one part above 0.9 amp would be like a line but transformed into a sine or some other curve.
How to do that?
Are you trying to fix [u]clipping[/u]? (Distorted flat-topped and flat-bottomed waves.)
You can try [u]Clip Fix Effect[/u]. But, it’s imperfect. When the wave is clipped information is permanently lost and it’s impossible to know the original shape or height of the waveform.
You can also try the Limiter Effect.
Digital clipping normally happens at exactly 0dB (1.0 or 100%) but you can get analog clipping (at the limits of whatever amplifier/preamp you’re using) or you can lower the level of a 0dB clipped file and the wave shape and distortion wont’ change but clipping at 0.9 will be “hidden” from audacity).
If you’re not trying to fix clipping, maybe you’re looking for a waveshaper.
https ://www.youtube.com/results?search_query=waveshaper+VST
Clip fix reduced amplitude but I can’t control it very well. I can’t cut above 0.9 precisely. It reduces whole range not just that above 0.9.
This does seems to get results I need. Is there an Audacity plugin ?
Waveshapers are creative tools to make sound weird, they’re not designed for repairs to make sound normal.
There are plenty of free VST plugin waveshapers which will work in Audacity in Windows.
Audacity’s “Distortion” effect is a waveshaper: https://manual.audacityteam.org/man/distortion.html
Also, the “Hard Clipping” and “Soft Clipping” options in the “Limiter” effect are waveshapers: https://manual.audacityteam.org/man/limiter.html
Ok, I’ll try. I’m trying to create this from 0:05 to 0:13. Could you tell me is there a better way to do this ?
https://youtu.be/haXvp8M9Cog?t=6
Clip fix reduced amplitude but I can’t control it very well. I can’t cut above 0.9 precisely. It reduces whole range not just that above 0.9.
Perhaps you should explain exactly what you’re trying to accomplish, or why or what the problem is, etc. You didn’t actually say if you’re trying to fix clipping.
Clip Fix is trying to restore clipped peaks so it’s trying to “push-up” and “smooth-over” the peaks. If you are clipping at 90% (about -0.9dB)* the new peaks may go over 100% (0dB). So there is an option to adjust the overall level down so it doesn’t get clipped again. Clipping is the result of the signal being too high so you normally would want to reduce the level.
Limiting is the opposite. It generally tries to “push-down” and “smooth-over” the peaks (usually to prevent hard-clipping when recording** or when amplifying digitally). Of course, limiting has to kick-in before you actually hit the limit so other slightly-lower peaks will be affected too. The Audacity limiter has a look-ahead and a “hold” setting (similar to the release-time on a compressor) to minimize the distortion (it tries to mostly maintain the wave shape). The Audacity version also has a make-up gain option to push the overall level back-up after knocking-down the peaks. In your case, you want to distort the waveform so a different, more traditional, limiter may work better.
None of this is going to be perfect.. It’s always best to avoid/prevent problems than to try and fix them later. 
Sometimes you can make the waveform “look better” without improving the sound or you may even make the sound worse!
You can create your own effects with the [u]Nyquist Programming Language[/u]. (I’ve done some programming, but I’ve never used Nyquist and I’ve never done any audio programming.) In general, programming is NOT easy but Nyquist is supposed to be relatively easy and manipulating amplitude levels is one of the easiest things you can do. However, it will be a more-tricky if you only want to “touch” the flattened waves.
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- Normally, we measure levels in dB (decibels) but clip-fix uses a combination of dB and percentage, so here are the formulas. It’s handy to set-up a spreadsheet:
dB = 20 x log(A/Aref) where A is the Amplitude and Aref is the reference. Or, 20 x log(Percentage/100).
Ratio = 10 to the power of (dB/20), or Percentage = 100 x (10 to the power of (dB/20)) or in Excel, Percentage =100 * POWER(10,dB/20)
** Audacity can’t do that. To prevent clipping of the analog-to-digital converter during recording you need a hardware limiter to limit/reduce the analog signal before it’s digitized.
This https://youtu.be/haXvp8M9Cog?t=8
You hear the jump and then sudden cut of the amplitude with some sinusoidal (maybe even asin(x) +bcos(x)+ log(x) ) change of the sound
GlitchMachine’s Fracture is a free plugin which can produce those types of sounds …
https://youtu.be/wl_YFwbYLHI?t=218
[ Fracture works in Audacity on Windows ]
Thank you. I’ll try.
I used Fracture but something it works sometimes it doesn’t. The output in preview is not he same as output in audacity windows.
Fracture silenced the sound completely which is not what I hear at preview.
Sometimes Audacity does that with VST plugins: the preview is similar but not the same as the result.
The only cure for that is to use another DAW which is more VST compatible.
NB: In Audacity when you review what applying the effect has done, you either have close the (Fracture) effect window,
or disable the effect, (uncheck the enable box), otherwise the effect will be applied again to the playback, (a double dose).
