Dolby SR
The Dolby SR (Spectral Recording) noise reduction format was developed by Dolby Laboratories and has been in common use in professional audio since 1986 and in-theater audio since the late 1980s. It is a revised version of Dolby's earlier formats, combining aspects of Dolby A, B and C (e.g., sliding band and fixed band companders) to improve the dynamic range (i.e., the range in decibels between peak level and noise floor) of analogue recordings and transmissions by as much as 25 dB. Dolby SR is used in many modern professional audio analogue (i.e., tape) recordings by recording and post-production engineers, broadcasters, and other audio professionals.