What does the term. Dolby B, or Dolby C. printed on tape recorders and other sound system refer to?

1. The terms 'Dolby B' or 'Dolby C' found printed on tape recorders and other sound systems refer to specific audio noise reduction systems developed by Dolby Laboratories. 2. These systems work by compressing the dynamic range of the audio signal during recording and expanding it during playback, which effectively reduces the audible level of tape hiss (noise) without significantly affecting the original sound quality. 3. Therefore, 'Dolby B' or 'Dolby C' refer to a Noise reduction circuit.