 Dolby Labs claimed that most members of the general public could not differentiate between the sound of a CD and a Dolby "S" encoded cassette.Dolby "S" mostly appeared on high-end audio equipment and was never widely used.Dolby "S" is much more resistant to playback problems caused by noise from the tape transport mechanism than Dolby C. Likewise, Dolby S was also claimed to have playback compatibility with Dolby B in that a Dolby S recording could be played back on older Dolby B equipment with some benefit being realized.