 Dolby noise-reduction system

A Dolby noise-reduction system, or Dolby NR, is one of a series of noise reduction systems developed by Dolby Laboratories for use in analog audio tape recording.The first was "Dolby A", a professional broadband noise reduction for recording studios in 1965, but the best-known is "Dolby B" (introduced 1968), a sliding band system for the consumer market, which helped make high fidelity practical on cassette tapes which used a relatively noisy tape size and speed.