Another is the Dolby noise-reduction system as used with magnetic tape.

The Deer Hunter was Cimino's first film to use Dolby noise-reduction system.

The Dolby noise-reduction system works by increasing the volume of low-level high-frequency sounds during recording and correspondingly reducing them during playback.

The introduction of the Dolby noise-reduction system narrowed the performance gap between cassettes and open-reel, and by 1973 the prerecorded open-reel offerings had almost completely disappeared, even from record stores and audio equipment shops.

According to Opton, the album was the first ever recorded using the Dolby NR system.

Compandors are used in concert audio systems and in some noise reduction schemes such as dbx and Dolby NR (all versions).

Dolby NR is the name given to a series of noise reduction systems developed by Dolby Laboratories for use in analog magnetic tape recording.

In the early-1970s, some expected Dolby NR to become normal in FM radio broadcasts and some tuners and amplifiers were manufactured with decoding circuitry.

In other words, Dolby NR is not becoming obsolete for analog recording, but analog recording itself is less prevalent as digital recording has become more widespread.

A number of noise reduction techniques can be used to reduce the impact of tape hiss, including Dolby NR and DBX, or, in case of video recording, frequency modulation of either the composite video signal, or the luminance part.