Removing crackling noises from audio

[C2 Scientist]

Hello all,

Lately I've been recording new engine sounds for Carmageddon, as you may have noticed from my recent gameplay videos. But when using my new engine sounds in-game, there's often a rapid 'crackling' noise that is bothering me. Hopefully there's someone knowledgeable enough in audio processing who can help me with this, because I was thinking of making a small pack of useful engine sounds - and perhaps some sillier ones as well. =P

Using Audacity, I typically apply a slight bass boost, then amplify a signal without clipping it. The most crackle-inducing part seems to be slowing down the audio (so that it fits better to the RPM range in-game). There seems to be two ways to do this: either the speed filter, or setting a different sampling rate. I'm assuming the latter doesn't actually re-process the audio in any way (unlike resample), instead it just sets how the audio is meant to played back. They seem to cause an equal amount of crackling, though.

One tip I read about suggested making sure that the audio starts and ends at 0.0 dB (at the looping point). However, the looping point crackling is not the problem here, because the crackling is rapid enough to be heard many times during a single loop.

If you want to do some tests of your own, here's an engine sound clip that crackles quite a lot in-game, after its volume has been increased and playback speed halved:

https://c2s.cwaboard.co.uk/DLoads/C2SMbVan1.wav


Cheers!

[jimbobbo]

What sample rate and bit depth is the original file? Are you saving it in the exact same format after processing?

[Deep_Blue]

*my* audio crackles, too. And I'm not using C2S's engine sounds.

[Deep_Blue]

I'll see what I can figure out. I use a lot of DSP in processing shortwave radio audio. I got yer sample.

*EDIT
Oh, wait....No I don't. There's a link but no file.