MR Noise is a broadband noise reduction processor. It distinguishes itself by being both great sounding and incredibly easy to use.
Like most noise reduction systems, MR noise works in the frequency domain, and requires that the noise spectrum be learned before noise reduction can commence. If your track starts with a bit of silence then MR Noise will work right out of the box, since by default MR Noise has the Learn parameter enabled, then when you hit play, MR Noise will learn the noise profile and start noise reduction.