Johns Hopkins Magazine - September 1996 Issue

Touch: In Short

A commanding glove

Operating computers through conventional means--like clicking on a mouse, or tapping a keyboard--requires users to know in some depth just how a system works, says Paul Schuster (PhD '87), senior staff scientist at Hopkins's Applied Physics Laboratory. Imagine, instead, if you could issue commands merely by pointing, bending, and wiggling your fingers.

Schuster has taken a glove used in virtual reality games, and added fiber optic cables and a magnetic tracking system to create a tool that can use hundreds of different hand and finger gestures to do just that. Two fingers extended and three curled means one thing, an open hand another. A white hand symbol appears on the screen, which tracks the glove's movements. To pick up an object on the screen, for example, the operator moves his gloved hand so that the symbol overlies the object, and then he makes a fist.

Schuster is part of a team developing intelligent systems that will help the Navy manage the rapidly increasing amount of data involved in operating its ships and submarines. The project, part of a larger endeavor to automate ship systems, is funded by the Defense Advanced Research Projects Agency.

Suppose, for example, that a Navy sub operator is reviewing a two-dimensional map of a tactical scene that includes symbols of aircrafts, surface ships, and submarines. Using the glove, the operator might point to and circle a symbol, in effect querying, "What are the most likely threats in this area?"

These days, "computer users are doing complex tasks with enormous consequences," says engineer Bruce Coury, the team's leader. "The last thing you want to think about is how to get a computer to do a task, or to try and remember, 'Where's that menu?'" With an intelligent system, he explains, technology "can be managed and used by far fewer people. The military is facing the same pressures as corporate America--demands to do more with fewer people."

Each finger of the glove contains a fiber optic cable, which has a light-emitting diode on one end and a photo-transistor on the other, explains Schuster. As a finger bends, it reduces the amount of light transmitted through the fiber optic cable in that finger. The amount of light received by the phototransistor is converted into a number, ranging from 0 to 255, which can then be translated into programming commands.

The position and motion of the hand are tracked by the magnetic emitter/receiver. The emitter, a small cube fastened to the back of the glove, and the receiver, a box that sits on top of the monitor, each generate a magnetic field. The computer translates the degree of alignment of the two fields into a programming command.
--Melissa Hendricks

Instrumental changes

Ginger Hildebrand draws a bow sharply across the strings of a reproduction baroque violin. Then she trades the violin for a contemporary model, takes in hand a modern bow, and repeats the stroke. This time the attack sounds sharper, edgier, and the volume is significantly louder. "You can really dig in and articulate," she says.

What Hildebrand (Peabody MM '88) has just demonstrated is the technological development of the violin and how that development has altered the way musicians play it. She and her husband, David, who teaches at Peabody, perform colonial American music up and down the Eastern seaboard. They have hands-on knowledge of how instruments have changed since the 18th century.

To make a point about the violin, Ginger Hildebrand lays the two bows on the floor, one above the other. The colonial-period bow is slightly convex; the contemporary bow is concave, with the wood dipping in toward the horsehair and holding it more taut. Furthermore, the neck of the newer instrument bends the strings over the violin's bridge at a more pronounced angle. All of this increases the instrument's dynamic range and the variety of sounds a fiddler can generate.

Next she takes up a baroque guitar, a replica of an instrument from around 1690 that was popular in colonial times. It's much smaller than a modern classical guitar, and strung with five pairs of strings. Because of its diminutive size and weaker internal bracing, it cannot produce the big, resonant sound of a modern guitar. "You can't get the same string tension," she says, "so it sounds plinky." The doubled strings also require a change in her right-hand technique. A classical guitarist usually plucks the string from its side, with the smooth edge of the fingernail. Hildebrand must use the fleshy part of her fingertip to pluck the tops of the double strings on the baroque instrument. As with the violin, this limits her attack.

David Hildebrand explains that the need for greater volume drove many of the technological changes in musical instruments. In colonial America, he says, music usually was performed in the intimate confines of a drawing room or a cabin. Before 1750, he says, public concerts that a middle-class person could afford to attend were rare. As impresarios realized, there was money to be made at larger venues, but to do so musicians needed to put out a bigger sound, prompting development of louder instruments.

For most colonial Americans, he says, the chance to hear music was a rare treat. "What if the only music you heard was on a once-every-four-months trip to a plantation?" he asks, then notes that audiences took for granted ballads that had 15 or more verses. Today, he says, that doesn't work, so he and and his wife shorten the ballads they perform.

"What would someone in your 20th-century audience be doing by the 12th verse?" he says. "Probably looking at his watch and thinking, 'I've got a fax coming in.'"
--Dale Keiger

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