Ploease excuse my nievity, in the screen grab attached, the peaks and lows for want of a better word are “flattened” unlike a normal track where they are vary. Is this clipping?
Its a radio broadcast track that I have downloaded and as yet havent made any changes to, except to quieten down the track using a nebative “amlify” value, it actually sounds fine as far as I cant tell, I just wanted to broaden my Audacity horizons so to speak and understand why this appears like it does, and actually what effect it has on a music track, distortion possibly…
Yes that looks like [u]clipping[/u] which is the most common kind of distortion. But, it could just be severe limiting which “pushes down” or “rounds-over” the peaks. Limiting doesn’t necessarily sound like distortion, or at least it’s not as “harsh” as hard-clipping. Audacity’s limiter actually has look-ahead so it doesn’t change/distort the wave shape.
Dynamic compression*, limiting, and sometimes intentional clipping are used to “win” the [u]Loudness War[/u].
Note that Audacity’s [u]Show Clipping[/u] is showing potential clipping when the peaks go over 0dB. It’s not looking at the wave shape and you can get false-positives or false-negatives. If you have clipping and you lower the volume you’ll “hide” the clipping from Audacity but that doesn’t fix the distortion.
And Audacity itself won’t clip (because it uses floating-point there are virtually no upper or lower limits). So for example, you can boost the bass and make Audacity show clipping, but it’s not clipped (yet) it’s just going over 0dB. As long as you lower the volume before exporting everything will be OK… Regular WAV files, CDs, ADCs, and DACs can’t go over 0dB… Some other formats can but you shouldn’t create a “final product” that goes over 0dB because the listener will clip his DAC if he plays it at “full digital volume”.
You can also get analog clipping if you crank-up the volume and try to get 110W out of a 100W amplifier, or you can overload a microphone preamp, etc.
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- Don’t confuse dynamic compression with file compression (like MP3). Some people think MP3 compresses the dynamics but it doesn’t. MP3 is lossy compression and it can “damage” the sound but it does NOT hurt the dynamics.
Dynamic compression reduces the dynamic range (or “dynamic contrast”) by making quiet parts louder and/or loud parts quieter. Most-often it’s used in two steps, first to push-down the loud parts and then “make-up gain” is used to bring-up the overall-average loudness and make “everything loud”. Limiting is a fast-kind of dynamic compression. Clipping is a bad-kind of dynamic compression. Automatic Volume Control is a slow-kind of dynamic compression.
Radio broadcasts have multi-band compression & limiting.
There are free plugins which do that … https://forum.audacityteam.org/t/free-v3-toneboosters-plugins/64538/3
Expander plugins can undo compression: adding back dynamic-range, (probably not the same as the pre-compression version though) .
Expander plugins can undo compression: adding back dynamic-range, (probably not the same as the pre-compression version though) .
Yeah… It can’t really be “reversed”.* You can make the wave look better but you can’t necessarily make it sound better.
The problem is, you don’t know the compressor settings and with multi-band compression there are more unknowns. Some (or all) of the tracks may have been compressed before mixing, so that’s impossible to undo. It’s also likely that some compression was done during mixing, and more-different compression done during mastering. Limiting and clipping is impossible to (accurately) reverse because even if you know the original settings it’s impossible to know the original height or shape of the wave.
Audacity’s Clip Fix effect is basically an “un-limiter”. I tried it once or twice on an “overprocessed” CD and although it made the waveform look better it didn’t fix the distorted sound. It might work better if you have “clean digital clipping”.
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- If you know the settings/parameters compression CAN be reversed (but not limiting or clipping) . DBX noise reduction (for analog tape) used “compansion” and I believe the same method was used for analog telephone. The signal is compressed before recording (or before transmission) and when it’s re-expanded you end-up with a better signal-to-noise ratio.
except to quieten down the track using a nebative “amlify” value
If you already pulled the waveforms down from 100% with Effect > Amplify, then the chances are terrific that the music has peak distortion damage or clipping. You can’t fix that later. The damage is built-in no matter where you put the volume controls.
As above, stations have this Loudness War thing where Everybody Knows loud performances are more desirable and sell better. So the louder the better. Distortion Sounds Loud. So as long as you don’t overdo it, music will sound bright, crisp, and loud.
And the only down side might be if you try to use the broadcast music for something else. It’s going to sound miles away from the original purchased music. Chances are good that the DJ voice is going to go through that processing, too, so everything matches.
Why did this question come up?
Koz