“... developments start with the desire of the developer to get what he... wants so that he can use it."
Dr. Ray Dolby
For most of the second half of the twentieth century, magnetic tape was used in the making of most audio recordings, but there was always some background noise present on them. This tape hiss, or "white noise," was most noticeable in quieter musical passages.
In 1965 electrical engineer Dr. Ray Dolby (b. 1933) proposed the first magnetic tape noise reduction system. The task was to improve the signal-to-noise ratio of the recording, reducing the level of hiss without affecting the quality of the sound. His approach was to "compand" (compress, then expand) the sound. During recording, an encoding circuit was inserted between the recording source and the tape recorder; this compressed the dynamic range of the recording. During playback, a decoding circuit was inserted between the tape
more...