BBC News - Audio pioneer Ray Dolby dies aged 80 (http://www.bbc.co.uk/news/world-us-canada-24075429)

He founded Dolby Labs, starting off with tape noise reduction for cassettes. With quite a bit of marketing genius, Dolby was able to get their brand on such cassettes, which mark has been identified with quality reproduction ever since, in video, film and cinema.

Actually his work started on the Dolby A systems created to allow relatively low spec film optical tracks and mag stripes to handle the increased dynamic range of sound mastered on tape in the 1960s. The A system had four frequency bands, each being compressed according to the content within them using the principles of wanted sounds masking the noise nearby frequencies. Dolby B came along just when cassette decks were being marketed as 'Hi-Fi' in the early seventies. This had a single band of compression starting above 1KHz which met the main weakness of audio tape running at 1 7/8 ips., i.e. a high noise floor. Expansion during playback was complementary so potentially, restoring the correct dynamic range with a lowered noise floor.
His other main contribution has more than a passing interest to many on this forum; Dolby Surround. His research into pshycho-accoustic perceptions of direction based on relative amplitude and time of arrival, enabled him to perfect a workable analogue system for spatial coding a four (later 5) channel surround stage through a two channel analogue medium such as video tape soundtracks. This was later updated into a digital implementation (AC3 or Dolby Digital) when DVD became the distribution medium of choice.
The fact that many know his name through the products of his work that have become household names is a tribute to his success.

Ray Dolby really put it all together, didn't he? He developed truly valuable technology, protected it well legally, and was able to get contracts signed that promoted his brand without the need for a traditional ad budget. That's firing on all cylinders (or should I say, "exciting all frequency bands.")

Hats off to a genius on many levels.

I have fond memories of making audio recordings from LP records onto chrome cassette and using Dolby "B" noise reduction. The newer cassette decks had the new Dolby "C" noise reduction.

Although in my youth, it seemed like the Dolby encoded recordings sounded better with the Dolby off on playback because the high frequencies were boosted. (Whatever happened to the competing DBX noise reduction?)

Even back then, there was arguments of which technology is better---just like today.

The last cassette recorder that I owned was a Sony with Dolby B, C & S as well as HX Pro. 'C' was better than 'B' in operation but too aggressive to use without de-emphasis on playback. 'S' was a better scheme as it performed well in itself and could also playback acceptably on a 'B' deck or even without any de-emphasis available.
HX pro however was a brilliant invention. It successfully dealt with the problem of low dynamic range of mag tape when run at low speeds as well as the phenomenon of high frequency signal erasure by the bias current. The secret was to modulate the bias in line with the level of HF signal amplitude after it had been through a 'Dolby-like' emphasis process. This prevented the HF driving the tape into the non-linear part of its B-H curves. The cassettes just had better performance than the basic tape spec.. This system was used by most commercial duplicators, giving better recordings than most home productions. Brilliant!