CX (noise reduction): History and Key Facts

CX is a noise reduction system for recorded analog audio. It was developed by CBS Laboratories (a division of CBS) in the late 1970s as a low-cost competitor to other noise reduction (NR) systems such as dbx disc and High-Com II, and was officially introduced in 1981. The name CX was derived from "Compatible eXpansion", a feature of the technique.

CX is a companding system: the dynamic range of the signal is reduced before being written to the medium, then recovered (expanded) afterwards. Such a combination reduces the effect of noise on the resulting signal and expands the dynamic range that can be practically used. Directly playing the recording without the corresponding expander still results in an acceptable sound, hence the claim of being compatible.

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