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Going with the flow: Digital audio's big problem

technofile  by al fasoldt

Columns and commentaries in a life-long dance with technology
 

Simple gray rule


Going with the flow: Digital audio's big problem
 

By Al Fasoldt

Copyright © 1989, The Syracuse Newspapers

When the transmission fell out of my 180,000-mile Camry a few weeks ago, I suddenly lost my wits and took a few test drives in new cars.

It was a sobering experience. The stickers on the windows reminded me that replacement transmissions, even fancy electronically actuated Japanese ones, are cheaper than new cars. And the dashboards reminded me of the last remaining problem of digital sound.

If the connection between high-tech new cars and high-annoyance digital audio seems unclear, let me tell you what I saw in the windshield of one of the cars I drove.

I saw two numbers suspended in space out in front of the car, in a sort of hologram. They were supposed to show me how fast I was going.

This was a "heads-up" display. The theory is that if you're able to see how fast you are going in numbers projected out in front of you, you won't have to look down at the instrument panel. Drivers can keep their heads up.

Not me. I kept looking down at the dashboard, desperate for a "real" speedometer—the kind with a dial and a pointer. I wanted an analog display, not a set of digits.

The problem with digital representation of speed or time is that you get no sense of continuous movement. I saw "47" out in front of me and then suddenly I saw "51." Did the car jump through hyperspace to go instantly from 47 mph to 51 mph?

Digital clocks cause a similar warping of reality. As I look down at my K mart pen-watch, it says the time is 9:36. It keeps saying that for quite a while. Then it changes its mind and says it's 9:37.

But my old-fashioned Timex tells me the truth. Three pointers move around the dial at different speeds. I can see at a glance that while two of the pointers seem to show that it is 9:36, the third one tells the real story:

Time is always flowing, moving from one second to the next-one nanosecond to the next, one infinitely short moment to the next.

Sound works the same way. Anything we hear is a continuous event that starts at one time and ends at another. Whether it's thunder or the Beatles wanting to hold our hands, sound isn't a bunch of on-again, off-again states like heads-up speedometers or digital watches. It's a constant flow of audible information.

Audio engineers know this, but they also know that the magic word in hi-fi these days is "digital." So instead of bringing back analog sound-in which the recording is a continuous wiggle in a groove, corresponding exactly to the sound that the microphones picked up-audio engineers are now trying another approach. They're making digital sound behave as if it were analog.

Components that handle this best-of-all-possible-worlds task were demonstrated at the Summer Consumer Electronics Show in Chicago. Two different ways of doing this were shown.

The first method relies on a mathematical cold shower. The latest compact disc players treat the digital signal to a bracing wake-up spray in the form of new calculations as the signal goes through the player.

The parts of the signal that represent the quietest sounds—where digital recordings have the greatest trouble being accurate—are shifted around so that the faintest whispers on the master tape come through almost as if they started out in analog form.

The second method uses a machinegun approach. The digits—called bits in both computer and audio terminology—are routed around the standard circuits and fired one after the other in a rapid stream. This "bit stream" is aimed at a conversion circuit that turns the pelting of all these bits into sound.

"Bitstream" technology could become the standard way of decoding digital recordings, some industry experts say. The sound it creates is excellent and it has a further advantage: It's cheap.

Other refinements are sure to come as engineers and circuit designers learn how to smooth the rough edges of digital sound. And each new development is likely to spur on a few more, as companies here and in Japan compete for a share of the market.

Unfortunately, progress in audio isn't likely to lead to a change in the auto industry, where digital speedometers are appearing on more and more cars.

Maybe the designers in Detroit and Tokyo need a few pointers themselves—the kind that move around a dial, the good old-fashioned way—before they get the message.


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