help getting rid of buzzing on audio

[slimwaffle]

The noise is gone from the sample you uploaded, Gale, but the soundtrack at the tail of it is destroyed. When I tried I lowered the sliders as low as they would go for all eq above 800 Hz. My file didn't sound like yours. It ended up a more muffled version of what it was, with just the soundtrack and unpleasant background noise lower and more compressed sounding. If it will help matters we can refer to it as crackling too.

[Gale Andrews]

You may as I suggested have to trade between brightness and crackle, or see if Robert has another version of his script. The recording is badly damaged, after all.


Gale

[kozikowski]

Is this file intended to have the irritating buzz in it or not?

AudioFile_bd2.wav

I'm at sea. slimwaffle complained about serious buzz and then Gale came back with a solution to the crackling. Then slim responded with a comment about the buzz.

Then Gale responded with an 800Hz rolloff sample inexplicably labeled
AudioFile_bd2_cut_above_8000Hz.wav

Anybody else expecting the March Hare to make an appearance?

Anybody else wishing a lot more of the show was available instead of the special-effect sound segment at the end?

Anybody else wishing we had a clip representing the actual complaint?

Koz

[Robert J. H.]

Sorry, the code was indeed for mono sounds, And there's a wrong step-size, thats why it speeds up. Here's the correct version:

Code: Select all

(defun noise-red (s)
  (snd-avg s 50 1 op-average))
(multichan-expand 'noise-red s) 

As you can see, the value is much higher than before.
You can choose a smaller value and simply repeat the process (ctrl-r).
I haven't any hiss either. I had such a shrill, whistling sound recently, but it was due to a bad 6.0 mm > 3.5 mm adapter in the line-out setup.

You should first use a noise gate to get rid of the noise inbetween the pauses. This has the advantage that the louder bright sounds are preserved at that stage. We than can look how many crackles are over and which are not enough masked by the louder sounds.
Here is a rough code example that illustrates this:

Code: Select all

(defun gate (s)
  (mult (s-max 0.01 
        (snd-oneshot (s-abs s) (db-to-linear -23) 
                     (/ 1000 *sound-srate*))) s))
(multichan-expand 'gate s) 

All sounds can pass that are louder than -23 dB, all others are attenuated by -40 db (the value 0.01)
There is only "stop and go" in this code, therefore you should really use the noise-gate on the wiki.
The threshold of -23 is rather high, but lower ones still allow some crackles to get through. However, we should aim for about -40 dB and less to preserve some dynamics and remove the remaining crackles with click removal or a similar tool.

[Gale Andrews]

I renamed my dull-sounding but crackle-fixed file, sorry.

Sorry, the code was indeed for mono sounds, And there's a wrong step-size, thats why it speeds up. Here's the correct version:

Code: Select all

(defun noise-red (s)
  (snd-avg s 50 1 op-average))
(multichan-expand 'noise-red s) 

This sounds a reasonably good compromise between crackle and brightness, and still has some quite audible signal between 600 and 900 Hz. Mine had little audible signal above 600 Hz because I was trying to eliminate all "crackle". In Robert's achieved signal, 1000 Hz is almost entirely removed, then there is some signal remaining between 1000 Hz and 2000 Hz (but much reduced in volume to about -60 dB, so hardly audible).

As you can see from the graph above the EQ Graphic Mode sliders, each slider is centred on its frequency and operates in a range outside that frequency, so reducing the 800 Hz slider actually reduces the volume between 600 Hz and just over 1000 Hz, with most reduction at 800 Hz.


Gale

[slimwaffle]

If I understand you correctly, Robert, you want me to run the second script and then run the first one? When I did that I got lots of sound drop outs (I also tried them in the order you wrote them and got the same drop outs. Kind of like it was too in the red and shorting out). I then tried the first script alone and that gets rid of most all of the crackling. It's a little more muffled than I was hoping for, but at least it doesn't sound compressed. Thank you. Is there anything to brighten the sound?

[Robert J. H.]

I've been looking for a way to get rid of the crackles that remain in the silent parts of the sound.
I've tried click-removal, but it seems to fail completely, even with extreme values.
It now came to my mind that I've already written a plug-in for extreme click sounds. I've modified it to work with stereo sounds and added a control for the attenuation level.
On Windows, it plays a preview of the sound that are removed. If you press the debug button, you can see how many blocks were found and how many of them were damped.
The effect won't affect continuous signals (like those at the end of your example). those sounds are defined by the threshold and distance controls.
You can tell the plug-in how wide the clicks are and how much their volume should be reduced (total elimination sounds weird and unpleasant).

Let me know if the plug-in was of any assistance and if it causes any problems.

silence-cleaner.ny

Version 1.1

(2.36 KiB) Downloaded 157 times

[Gale Andrews]

Curiously, Effect > Noise Removal working on only a small selection of the noise gets rid of the noise quite well if applied with high "Noise Reduction" and "Sensitivity" settings (or applied a few times).

Noise Reduction barely harms the sound track audio (in the fragment that was submitted) because the distortion in that seemed to be created by the signal itself.


Gale

[slimwaffle]

Sorry for the delayed response. Again, thanks Gale and Robert for the help. Robert, the silence cleaner plug-in causes Audacity to crash every time I try to process the file. I'm using version 2.0.3 on Windows 7 x64 SP1. And Gale, using the noise removal effect with noise removal and sensitivity high gets rid of the noise, pretty much totally (with smoothing set high it seems to remove the tinny low-but rate sound too). The volume sort of fluctuates doing this though. I'm not sure how to accurately describe it. It sort of pulses lower and higher.

[Robert J. H.]

Does the cleaner plug-in play the preview or does it get stuck during execution?
Does it function on short sections (10 s or so).
Try it with the debug mode, maybe there will be additional information be given.
It may well be that it doesn't work with longer selections, due to stack overflow.

(2 minutes later)

I've tried it with a 7 min recording in stereo and it works perfectly well, even with preview on.
I am on a similar system as you (W7 AMD 64).
Have you tried it with another file?
I've no idea why Audacity should crash on every single attempt. I am very sad and sorry.