X-Noise.

X-Noise works from a noiseprint, a sample of the unwanted sound taken from a quiet passage, which it then subtracts across the whole recording. That approach suits constant noise, tape hiss, air conditioning, computer noise and preamp hiss on a vocal. The controls are laid out like a dynamics processor, threshold and reduction setting how much goes, attack and release smoothing how it behaves. It handles tracks, full mixes and damaged recordings.