How do noise suppression systems like NoNOISE and CEDAR work?
Digital techniques have been applied to many facets of sound processing and recording and have, on the whole, been found to give results far superior to their analogue counterparts. Nowhere is this more true than in the field of audio restoration, where excellent processes have been developed for removal of impulsive noise (thumps, clicks and ticks) and attenuation of continuous broadband noise (such as tape hiss). Example techniques for these two are outlined below. IMPULSIVE NOISE In this category we include many types of disturbance, from the click generated by a scratch on a 78rpm disc, to the tiny tick created by a single corrupt bit in a digital data stream. Also included is crackly surface noise from 78’s (that sounds like a frying pan), though this requires somewhat different treatment; however the outline presented below is fairly similar for both processes. Typically, audible clicks are of a few microseconds to a few milliseconds in duration, and their density can be up to a
