1998 Discover Technology Awards: Sound

Wednesday, July 01, 1998
Digital recording is a music lover's dream but a music company's nightmare. Since it offers essentially perfect reproduction--on compact discs, digital audiotapes, digital video discs, or even on music sent across the Internet--audiophiles can accumulate vast collections of music, transferring it from one format to another, copying it, and digitally altering it with little effort and no damage to the sound's quality. The same capabilities, however, make it easier for fans to avoid paying royalties to recording companies and artists. Joseph Winograd thinks he's found a way to protect the copyrights of digital music.

Ideally, music companies would like to permanently mark recordings as their own, and perhaps even hide a code in the music that would instruct recording devices not to reproduce it. Pirates could easily isolate and destroy such a code if it's inserted before or after the music, and inserting the code in the body of the recording would blemish the music. "The idea of hiding copyright and other information in music has been looked at for close to two decades," Winograd says, "but the codes were always audible to the listener." Three years ago Winograd, who is vice president of engineering at Aris Technologies in Cambridge, Massachusetts, set out to crack this problem. By analyzing what parts of the digital signal the human ear notices and what it ignores, he came up with a way to encode information by subtly modifying the ignored parts of the signal to generate a mathematically derived pattern. A computer monitoring the digital 0's and 1's of the music can spot the inserted code, but a human listener cannot.

Polygram Records began making cds with Winograd's digital watermarks in February. Royalty collection societies will be the first to electronically monitor songs being played on the radio and bill radio stations accordingly for royalties. The code may also be useful for storing all sorts of hidden information in music signals. Eventually, Winograd says, music companies might encode the name of the artist and song so that the information could pop up on a display on your radio, even though the DJ didn't bother to tell you.




FINALISTS

Be Flat
Noise Cancellation Technologies' Gekko Flat Speakers
Innovator: Michael Parrella

Michael Parrella's eureka moment came when a room-size power transformer suddenly started playing a Beatles tune. Parrella, president of Noise Cancellation Technologies in Stamford, Connecticut, had been hired by an electric utility company to do something about the deafening hum of its transformers, which control power going out the lines. Attached to the metal walls of one transformer were dozens of small, flat transducers made of a ceramic that is piezoelectric--it vibrates when an electric signal is applied. The transducers were intended to vibrate and cancel the transformer's noise, but Parrella, in a playful mood, decided, while the transformer was turned off, to feed some fm radio through the transducers to see what would happen. "All of a sudden, we heard music," he remembers. "It wasn't great sound, but it wasn't bad."

Parrella set out to create a whole new kind of high-performance speaker from piezoelectric material. First he redesigned the transducers so they vibrated efficiently across the whole range of frequencies that make up audible sound, rather than just those in a transformer's hum. And he used a plastic to play the role of the transformer's steel walls, vibrating in response to the transducers and creating sound.

In January 1997, Parrella unveiled his Gekko Flat Speakers. While most conventional speakers have a "sweet spot," a small area in the room where the sound from two stereo speakers is balanced, the Gekko speakers emit sound evenly in all directions, so the sweet spot takes up most of the room--Parrella calls it a sweet space. In addition, the speakers are only two inches thick, which means you can hang them on the wall. They cost from $149 to $499, depending on size.




Live Sound
True Dimensional Sound's Harmonic Enhancement Technology
Innovator: Arturo Garcia

Many audiophiles shell out big bucks on home stereos in the hope that their recordings will sound just like live performances. But every recording engineer knows that this is an impossible goal. No matter how precise the recording equipment or perfect the reproduction, what sounds great in the studio can fall short in the living room.

A few years ago, Arturo Garcia looked up some research from the 1930s on the way people perceive sound. It showed not only that humans tend to enhance certain frequencies at the expense of others, but that they do this differently according to many factors, such as the loudness of the music or how the sound interacts with the room in which they're listening. "The human brain perceives each acoustic environment in a different way," he says. "That's why if something is recorded in one place and played back in another, it won't sound the same."

Garcia promptly rigged up electronic circuitry that modified the sound coming from a stereo in ways suggested by the earlier research. After tinkering for several years, he wound up with a simple coiled circuit much like a transformer, which, when attached to a stereo, has the effect of bringing out details in the music and making it seem "closer," which Garcia calls an enveloping effect.

In April 1997 he and his colleagues at True Dimensional Sound in Coral Gables, Florida, began selling the boxes starting at $195 (a high-quality audiophile version costs $1,200). The technology is not restricted to these stereo attachments--it can also be used in theaters, jukeboxes, and computers, and it can be incorporated into recordings. Thus far, the technology has been used for several film sound tracks. Garcia is now negotiating with manufacturers to build the circuitry right into speakers.




A Muffler for Supersonic Jets
University of California at Irvine's Virtual Shroud
Innovator: Dimitri Papamoschou

Each time the supersonic Concorde takes off for London or Paris from John F. Kennedy International Airport in New York, it says good-bye with a crashing wall of noise, even though the plane itself has not yet exceeded the speed of sound. The source of that blare, explains Dimitri Papamoschou, is the jet's supersonic exhaust. As the hot gases leave the engines and hit the surrounding air, they create turbulent eddies, which can reach twice the speed of sound. The eddies act like a stream of Mach 2 bullets, Papamoschou says, each creating shock waves--and sonic booms--as it twists and turns back from the engine. "These shock waves are the strongest source of noise for exhausts like these," he says.

Because of that sonic blare, supersonic planes are limited to a few airports; the noise also threatens the potential usefulness of nasa's high-speed civil transport plane. So five years ago Papamoschou, an aerospace engineer at the University of California at Irvine, set out to dampen the din of supersonic exhaust without hurting the efficiency of the jet engine. In January 1997 he received a patent on an invention that does exactly that--he calls it the Virtual Shroud.

Papamoschou buffers the supersonic exhaust by surrounding it with a stream of slower-moving air. Even though the eddies from the exhaust are supersonic relative to the ambient air, they are subsonic with respect to the air in the buffer zone. Therefore, they make less noise--90 percent less, according to laboratory tests. "We do have to make sure the additional flow does not create its own shock waves," Papamoschou says. Right now he is trying to cut down on the amount of additional fuel the shroud uses and to eliminate even more exhaust noise. He is also working with nasa to design a quieter engine for the next generation of supersonic planes.
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