Custom click removal?

Special Interest Groups Audio Processing
1

Hi, I’ve recorded 10 hours of a course on project management, however much of it has tiny clicks throughout, I think just from my voice.

Short excerpt: https://soundcloud.com/user-524851913/click-example1

I’ve tried the click removal feature in Audacity, but depending on settings it does not find them, or degrades the audio. The clicks are so tiny, but in some sections so many.

Is there some way to create some kind of custom filter or process that targets just these tiny clicks?

Thanks much,
Bill

2

There is a free DeClicker plugin for Audacity which will automatically remove clicks, here.

The DeClicker settings used.png
Now the bad news, that plugin is slow: at the settings required, (shown above), processing-time is about double the playback-time , (on my computer, YMMV). Also that plugin may choke on audio which is hours long, you’ll have to apply it in installments, (Try 15 minute chunks, then see if you can get away with longer sections).

The code below if put into Nyquist prompt removes the mains-hum, (no effect on clicks)

(setf *track* (notch2 *track* 43 5))
(setf *track* (notch2 *track* 60 10))
(setf *track* (notch2 *track* 90 10))
(setf *track* (notch2 *track* 212 10))
(highpass8 *track*  20)

Notch filters used to remove deep hum (no effect on clicks).png

3

Thanks much, the clicks are removed.

However, their is some addition of “rumble” in the audio. Any ideas what settings to play with to avoid that?

4

I think you mean the bassy hum …

Constant hum shown on Audacity spectrogram.png
Constant hum shown on Audacity spectrogram.png698×598 196 KB

That’s 60Hz mains-hum and some other constant low-frequency signals, (and combinations thereof).
You can get rid of them with the notch-filter code shown in my previous post.
Paste the code into Audacity’s Nyquist Prompt, (which is in the effects menu),
then apply Nyquist Prompt to the Audio like any other Audacity effect.




If you still hear rumble after removing the hum, try this “100Hz rumble” filter in Audacity’s equalizer.

100Hz Rumble filter curve in Audacity's equalizer.png
100Hz Rumble filter curve in Audacity's equalizer.png1177×563 19.9 KB

100Hz Rumble filter.XML (496 Bytes)

5

Great plug-ins. I echo all the other congratulations.

You changed three things from the defaults - interesting, could you say your thinking?

  • Step size changed from 5 ms to 3 ms.
  • Minimum time between clicks (steps) changed from 3 to 2.
  • Test frequency minimum changed from 150 Hz to 5000 Hz.

You’ve also changed the test frequency maximum from 9600 to 15000, but think I understand that: although few can hear above 9600, why not be thorough, since high frequencies don’t take as much computing time as low frequencies.

6

Can I also ask your opinion on the order of processing? From experimenting, it seems to me the following is the right order, but being new to all this, I am not sure:

  1. Run 100Hz rumble first, because that fixes the “p” pop plosives sounds. And because if I don’t run it first, there are some big spikes in the audio that reduce the effectiveness of the following normalization step.

  2. Run normalization, making the audio clips much louder (and better).

  3. Run the DeClicker.

I do not run compression, as to my untrained ear it distorts the emphasis I try for in the audio. Does this seem like a sensible choice (if not, it would be great to get your input as to why)?

7

The mouth clicks are ~3ms in duration, 5ms step size would not remove them,
(the shorter the step size, the longer the processing time ).

The mouth clicks are all above 5000Hz …

mouth clicks are 5000kHz-16000kHz.png
mouth clicks are 5000kHz-16000kHz.png1288×603 215 KB

You could DeClick the entire audio spectrum, 20Hz-20000Hz , but with that plugin, set at 3ms steps, processing-time would be tens of times the playback-time.

You can increase the maximum from 15000Hz to the full 16000 Hz, there will be an increase in processing time, but I don’t think anyone will be able to hear any improvement.

8

Definitely run the rumble filter first : it gets rid of infrasound, which you can’t hear, but which causes problems when processing the waveform

Any loud spikes can be attenuated using Audacity’s (soft) limiter …
Audacity (soft) limiter (with make-up gain selected).gif
If you select “apply make-up gain” in the limiter you won’t need to run normalization to 0dB.

9

Thanks much, very good advice. Got it working well.

I found the “Isolate” option very useful to see what it was going to remove, convincing me the settings you provide work great, without taking out too much.

Very recommended as a standard step for any voice processing.

(Suggest it be included with the default Audacity plug-ins.)

10

Thanks for the thread. I am working on restoring a 1965 Rolling Stones recording and the de-clicker worked wonders.