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 - sudden white and black pixels, which remind one of salt and pepper sprinkled over a photo. This is done after demosaicing.
Whereas salt-and-pepper noise is typically just white or black, hot pixels can be of a pure, saturated color, while dead pixels are black. Hot and dead pixels occur for a very different reason than salt-and-pepper noise and should be handled using the Hot/Dead Pixel Filter, which works before demosaicing.
The slider adjusts the threshold which must be exceeded for the suppression to be applied.