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How one man changed the face of audio

technofile  by al fasoldt

Columns and commentaries in a life-long dance with technology
 

Simple gray rule


How one man changed the face of audio
 

By Al Fasoldt

Copyright © 1987, The Syracuse Newspapers

A quiz: Who has what is probably the best-known name among all inventors of the second half of the 20th Century?

A further puzzle: Most people don't even know the man exists.

A tough one, eh? Here are a few hints. This man is usually not even thought of as an inventor. By profession, he is an electronics engineer.

The item that he developed isn't a device in the standard sense of the word, but a circuit. Actually, so far he has come up with three varieties of this circuit, each bearing his name.

Millions upon millions of objects that make use of his circuit have been sold. The most common of these objects is small enough to fit in a shirt pocket. The biggest can only fit in studios.

Give up? Hold your curiosity. Let me back up a bit first, about 25 years.

Back then, a young electrical engineer became intensely dissatisfied with the tape recordings that he and others had been making.

Tape recordings had rapidly replaced transcription discs for studio use as soon as the first tape machines were brought back from Germany after World War 2. They made recording much easier, since tape could be cut and then pasted back together to edit out mistakes.

But in one area tape was a definite letdown. All the recordings made on the newfangled magnetic recorders were plagued by a rushing noise called hiss.

This hiss was a result of the very nature of the way tape recorders worked, and everyone thought nothing could be done about it.

The hiss came from the millions of magnetic particles that pass by the recorder's playback head. Behind the music would be the "signature" of each tiny magnetic particle. Put them together by the millions, and the engineers got hiss.

One way to reduce this noise was to speed up the tape. The faster those little particles went zipping by, the higher the pitch of the noise. Eventually, if the speed was fast enough - about 30 inches per second - the pitch of the hiss is too high to hear.

But a speed of 30 inches per second is out of the question for home use, since a recorder capable of a 45-minute playing time would have to hold a reel of tape the size of a garbage-can lid.

Our dissatisfied engineer knew that the others were right - nothing, indeed, could be done to change the tape recorder to get rid of this curtain of hiss.

For most minds, that would have been the end of it. But great inventions are often produced in a meandering way. Our man zagged while everyone else zigged.

He left the recorder alone and began tinkering with the signal coming into the recorder. He knew from previous research that the human ear is notoriously lazy when it comes to hearing quiet sounds when something louder is sounding at the same time.

The effect is familiar. If the neighbor's dog is barking outside, we turn up the radio and no longer hear it. In the shower, the rushing hiss of the water keeps us from hearing the phone.

Suppose things were reversed? Suppose the phone rang loud enough to keep us from hearing the rushing hiss of the shower?

Suppose the music was loud enough to keep us from hearing the hiss of the tape recorder? To our lazy ears, the hiss would not be there at all.

This would mean, our engineer realized, that any time the music was loud enough, the hiss would just plain disappear. But he saw how he could extend this concept to make hiss disappear during quiet passages, too.

He realized that if, during recording, he made the quiet passages louder than the hiss, he could then reverse everything during playback. In a mirror-image process, the same circuit that made the quiet sounds louder would make all these boosted sounds quieter when the music was played back.

Anything that wasn't part of this mirror-image boost-and-cut deal wouldn't get reciprocal treatment. And the thing that definitely wasn't part of the deal was hiss.

In other words, hiss that was already on the tape would be made quieter when the playback circuit brought the formerly quiet sounds back down to their previous level.

In one clever circuit, he had achieved what everyone else had thought was impossible. He designed one version of this noise-reduction circuit to sell to studios. It became known as the "A" system.

The next circuit, made simpler for use in consumer recorders, was called the "B" system. And a third circuit, recently introduced, is called, logically enough, the "C" system.

Without this invention, the tiny audio cassette could not have challenged the LP record as the most preferred way of listening to music. And there might not have been Walkman players and boom boxes.

So the next time you pop a prerecorded tape into your cassette deck, take a look at the little "Double-D" symbol on the tape or on the recorder. And somewhere on the tape and on the machine you'll see Ray Dolby's name. If it weren't for Ray and for our lazy ears, life might just be a lot noisier.


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