Impulse Noise Reduction
The effects of this tool are only visible at a preview scale of 1:1 or more. Use a detail window (click on the icon under the main preview panel) to inspect a part of the image, or zoom the main preview to 100% (also called 1:1) .
Suppresses 'salt and pepper' noise - usually white single-pixel noise, similar (but not occurring for the same reason as) hot or dead pixels. The slider adjusts the threshold that must be exceeded for the suppression to be applied.