Topic: How to fix 'crackling' sounds (i.e. static noise) in recordings?

[mysterymadman]

Hiya,

Last year I taped my first major show (being Depeche Mode at the Ahoy, The Netherlands) and back then I post processed it. However... this was also my first post processing effort, and last December (when being much more experienced in post processing) I came to realise that I had made some major errors on the DM show, so I decided to do the post processing all over, and at present I am at that, and I have run into a nasty situation for which I have yet to find a good fix.

The main issue is most likely caused by the very poor "el cheapo" 3 Euro mic I used for the recording (which, back then, was all I managed to find in time, and which has now been discontinued, in favour of a Sony ECM-717). Not all too surprisingly so, the mic has picked up a lot of static noise (or so I presume it is), and it causes the recording to sound very raw and 'crackling'. I have put up a +/- 40 seconds sample of it at http://www.millennics.com/test/dmbad.wav (+/- 7.7 MB in size).

Now, if you look at the waveforms, you'll readily see that it is very spiky (fortunately not all of the recording came out like this, but at least some 6 or so songs suffer heavily from this), and when playing it back it sounds plainly bad to me (ignore the somewhat muffled sound, this will be taken care of later).

I use Sony's Sound Forge v8.0d for post processing, and I have not yet been able to find a good filter or other way of making this sound better. What I would kinda like, is a filter (or so), that makes the recording sound somewhat more 'polished' and removes the crackling sound.
I tried soft compressing it somewhat, but that didn't do enough magic for my likings. The Wave Hammer works great for bigger spikes (with or without a soft limiting pass included), but often the spikes are not so loud, and consequently it is difficult to set up a good 'selective' wave hammer setting that leaves the desired loud parts alone)...

Can anyone give me some suggestions as to how I could improve this particular aspect of the recording (if need be with additional filters)?

Tnx in advance, and cheers!
MM

[mysterymadman]

I forgot to mention previously that I did already use Sony's vinyl restoration filter, and that did get rid of a lot of the major pops that were present in the initial recording. However, I hope someone wants to have a listen to the sample I put up, and throw in their 2 cents...

Anyone?

Cheers,
MM

[gratefulphish]

I downloaded it, and looked at it in SF8.  You can see the crackling in the waveform when you zoom in most of the way.  Not sure what caused it, but the forms are somewhat irregular, so I don't know if any "filtering" is really going to help. Depending on how much you care about the recording, you can always manually go in and either copy channels, or cut the crackles out.

[xargos]

I have to agree that filtering might not do much for you at this point.  When I have come across any similar crackling before I have usually ended up either having to live with it or edit it out manually.

There is one filtering method that I have had mixed results with.  Using one of the latest 1.3 series beta versions of Audacity, you can try the "repair" tool.  The tool allows you to select very short segments of audio (only about the length of your average crackle) and smooth them out.  It basically brings the selected segment in line with the waveform surrounding it.  In some cases this can greatly lessen the effect of the noise, but in other cases it doesn't.  Using the tool is time consuming, but depending on how much work you want to put in it might be worth trying.

The only thing I should mention is that in the beta versions of Audacity you should be doubly sure to save edits often.  I have found them prone to crashing on one of my computers, so I use non-beta versions for pretty much anything but the repair tool.

[mysterymadman]

Hi,

Tnx for the great advice!
On my previous machine I did indeed use Audacity 1.3 beta (don't remember the exact version from the top of my head, but I think it was 1.3.2), and I'll give that a go on the new machine too. Basically what you describe as the way the audio repair tool works, is what I normally do manually (in SF), using the "interpolate" tool. Could be handy to have the software do that automatically, and indeed this can help a lot in clearing up the sound (I normally use this method on the big spikes).

Well then, tnx again, and I see you guys came to the very conclusion I already feared: filtering will be difficult... Bummer...
But... at least I'll give Audacity another go.

Cheerz,
MM