I use v3.3.3 under Win10 to record spoken audio at 24 bit 48000 through a Focusrite Solo. When I yell into the mic to deliberately create clipping, the waveform looks clipped, as proved by the fact that after de-amplifying enough to show the full wave in the track, wave peaks are crew-cut flat. However, ACX check shows Peak Volume = -.07db (just below clipping) and Find Clipping yields nothing regardless of the number of samples specified for Start & Stop threshold. A downside is that I can’t easily distinguish with Find Clipping between truly-unclipped and quasi-or fully- clipped waveforms, so may fail to satisfy a client who doesn’t want flat-topped waveforms.
Why does Audacity show this waveform as NOT clipped when it clearly is? It seems like some automatic limiter is in effect though I can’t find it. What’s going on?
That’s weird… The ADC (inside the interface) should clip at EXACTLY 0dB. Sample rate conversion can make a difference (it’s “imperfect”) but I don’t think that’s happening at 48kHz. Maybe there’s a small bug/defect in the Focusrite?
Is the LED on the Focusrite showing red? It should “know”. And you’re probably not hitting -0.07dB without clipping anyway.
But really, you should be leaving some headroom to prevent accidental clipping. If it only happens when you yell into the mic, it’s not a problem. Just for reference, pros typically record around -12 to -18dB. You probably don’t need THAT much headroom unless your sound levels are highly-unpredictable, but digital recording levels are not critical.
Audacity is not analyzing the wave shape. It’s just measuring the peaks and indicating potential clipping.
You can get a false negative by reducing the volume of a clipped waveform to peak below 0dB (like what you have).
You can get a false positive by running the Amplify effect (or by boosting the bass, etc.) and pushing the peaks over 0dB. Audacity uses floating-point internally, which virtually has no limits, but it will still “show red”. If you export as a regular integer) WAV file, it will be clipped, or if you play it at “full digital volume” you’ll clip your DAC. If you lower the volume before exporting and it’s not really clipped it will be OK.
ACX-Check’s job is to show you when your audiobook chapter’s peaks and tips are quieter than -3dB, and your RMS (Overall Loudness) is between -18dB (louder) and -23dB (quieter). It’s not a universal sound analysis tool.
We should be careful with the “clipping” label. Many stereo microphone interfaces will cheerfully mix your one production voice down to single channel mono, but give you clipping at -6dB.
You should not be spending any time snuggling up against 0dB.
As above, Audacity doesn’t overload, so you can truck along editing happily and be fine until you tried to export the client’s sound files.
In The Wild, there is nothing louder than 0dB (don’t fall in love with MP3), so the best the measurement instruments can do is work in the subjunctive.
“This waveform would have exceeded zero dB had it really wanted to.” Whether it did or not is unknown.
