24 channel Dolby noise reduction, (signal processing system). Dolby SR or A.
Dolby noise reduction card developed in 1986 to improve the the range in decibels between peak level and noise floor. It is used as the optical analog format on almost all 35mm film release prints. Used now for vocal processing.
DBX Type 1. Vintage noise reduction.
Desk top, "Miracle" noise eleminator.