Noise in renderings is a common problem,the only real solution to which seems to be for us to increase the number of samples (and ,therefore,rendering times as well)
Recently a Despeckle node has been added on compositor for making possible for us to fix the noise issue using compositing techniques (which should result into some faster renderings)
In this video tutorial we’re going even farther and suggesting a simple,easy to setup combination of nodes that could,hopefully,reduce the noise,in most of the cases,while keeping ,at the same time,rendering times low
Here is the link to this video tutorial :
Hope you’ll enjoy this!