The elimination of crackle can be done automatically or manually. The problem of using filters that automatically remove the crackle is that many times the filter, if it is inadequately configured, also removes parts of the song, leaving the sound muffled or "metallic" (with a little echo). If the recorded sound does not have crackle, there is no need to use this filter, and you go straight to the next step, which is separating the recorded songs in a single Wav file into many distinct Wav files.

You can try using the filter "Sonic Foundry Click and Crackle Removal" from the menu DirectX of the Sound Forge. Use the option Preview to check if the filter will work as you wish. Try to alter the preset filter to see if the result improves. In our tests, we have achieved more success by using the preset 2 (putting the "Click removal 2" in the field Preset). You can also try other programs for the crackle automatic removal, such as the DePopper we mentioned on previous page.

If the number of crackles is low, you can simply remove them manually, which usually gives better final quality. The process is simple and consists in selecting the crackle and applying the filter Sonic Foundry Click and Crackle Removal of the Sound Forge just in the selected area. By doing so, only the crackle is really eliminated and you make sure the rest of the song will not be muffled or "metallic", since the filter will be applied only on the crackle.

On Figure 12 (you should click on it to see exactly what we are explaining), we clearly see a big crackle in the right channel. In general, crackles are easily seen as the one in the figure. Just select the area of the crackle with the mouse and apply the filter for it to be gone.

click to enlarge
Figure 12: Big crackle.

For smaller crackles, just put the Wav file to run and stop the execution in the moment you hear a crackle (do not forget to keep on following the cursor which indicates the part of the song which is being executed for you to be able to visualize a little where the crackle is). After that, mark the area that has just been played and apply a zoom. You will clearly see the crackle. See, in the next figure, an example where we have a small crackle at the beginning of a selected part (above, left channel) and a crackle a little bigger in the right channel, approximately in the middle of the selected part. Just select each crackle and apply the filter for the crackle to be gone.

click to enlarge
Figure 13: Two small crackles.

The removal of crackles can be a really difficult process, especially if the recorded LP has many crackles and you cannot manage to make any automatic crackle removal filter work properly, that is, if the filter is making the sound lose quality (gets muffled or "metallic").