1994 : Dolby Digital Story

The 1994 movie 1942: A Love Story was a landmark in Indian cinema in many ways. It had the last piece of music by the legendary R.D. Burman. It was, incidentally, also the first Indian film to be given a U/A rating! It was also famous for a reason lesser known – for being a stepping stone in following latest trends in sound engineering. It was the first Indian movie to use Dolby Sound. The logo of Dolby sound was seen in almost all movies that came after this, and yet still very few know what this Dolby Sound is.

Scientifically, Dolby Digital is the marketing name for a series of audio compression techniques developed by the U.S. based Dolby Laboratories started by Ray Dolby. One of the most popular audio formats, it is manufactured under various names like Dolby Digital 5.1, Dolby AC-3, and Dolby SR-D. To a layman, this may sound like any other scientific gibberish but let me try and simplify it. First question which would come to someone’s mind would be – what is Dolby all about? If you compare your ordinary acoustical surroundings to what you hear on the television or a cinema theatre, you would observe that there is a lot of sound in the background under ordinary circumstances, whereas the movies have a perfect sound. This effect of reduction of noise has been obtained by using a noise-reduction format which is Dolby Sound. Dolby Labs’ first product was manufactured for record companies, but later, Dolby enhanced his product, a compander called Type A: Dolby Noise Reduction, to improve movie sound. As the corporation’s history explains:

“Dolby found that many of the limitations in optical sound stemmed directly from its significantly high background noise. To filter this noise, the high-frequency response of theatre playback systems was deliberately curtailed… To make matters worse, to increase dialogue intelligibility over such systems, sound mixers were recording soundtracks with such high-frequency pre-emphasis that high distortion resulted.”

Thus, Dolby developed a digital sound compression scheme we now know as Dolby Digital. This was a feature first used in the 1992 Batman Returns in Hollywood and then it came in 1994 to India.

The working of Dolby sound can be explained simply. The Dolby Digital reader mounts on top of the projector and scans the film as it passes through. The light from an LED (Light Emitting Diode) shines through the film onto a CCD. The image, containing little specks that represent 1s and spaces that represent 0s, is sent by the reader to a Dolby Digital Processor unit that turns the binary data back into sound. And thereby we get Dolby ‘enhanced’ sound!

We may not have given it much notice, but the Dolby systems surround us! Let us see how…

It is used in recording all cassettes. It is used in noise reduction system for FM broadcast radio. It is in all DVDs (look out for the logo on your DVD covers!). We have new headphones coming up which stimulate to expand stereo content to surround sound. Its technology is being used effectively in audio enhancement.

The understanding of the effect of audio is absolutely essential in film making. Imagine watching a movie in which you cannot decipher the dialogues? Hence, the need for sound compression techniques like Dolby Digital. Thus, one of the most important people backstage is the Sound engineer. I guess this is another interesting career option for the engineers reading this.

Ayushi Uberoi

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