Travelers of the future may still carry foreign-language phrase books. But in a few years they may also load software onto their pocket computers that permits real-time, simple conversations with their foreign hosts.
Prototypes of such portable translators are being tested by the US Army and Navy, and others. In these new systems, the sentences are simple, the syntax is far from perfect, and the speech synthesizers get all the good lines. Decades of research in linguistics coupled to increasingly powerful computers has yielded systems that actually let two people who speak different languages pop on their headsets, plug into their computers and strike up a conversation. In April, the Army went to Zagreb, Croatia, to try out just such a system: a portable translator that lets English and Croatian speakers talk with each other.
Such conversation is highly complex: the computer must dovetail programs to recognize English speech and translate it on the spot, then produce it in Croatian on the speech synthesizer. That is only half the battle: once the Croatian understands the synthesizer and responds aloud, the system must work in reverse, recognizing and translating the words back into English and voicing them through the synthesizer.
"I wasn't sure we could pull it off," said Robert E. Frederking, a machine-translation researcher who led the Carnegie Mellon University team working on the project.
Frederking, who accompanied the army group to Zagreb, said the system could not cope with discussions of molecular biology, 12-tone music or the latest movies. "But in the contexts we designed it for, it was functional," he said.
"There were plenty of mistakes," Frederking said, and the system worked better with someone like himself, trained to expect it to err from time to time.
"But even when it couldn't translate a particular word," he said, "we could often get the gist anyway."
The army chaplaincy financed the Zagreb project to see if portable machine translators could help chaplains do their jobs better not only during wars, but also on peacekeeping and humanitarian missions, said Chaplain Mark Nordstrom.
Nordstrom heads the project from the US Army Chaplain Center and School in Fort Jackson, South Carolina.
"At times, we're required to be in the villages," he said, "and often there are not enough human translators to go around."
The language software for the Zagreb prototype was developed in Pittsburgh by Carnegie Mellon, which has long been interested in machine translation.
Lockheed Martin did the system integration, handling the user interface for the Toshiba Libretto laptops that fit into the cargo pockets of army uniforms.
Alan Black, a computer scientist at Carnegie Mellon, worked closely on the Zagreb system. Carnegie Mellon has its own speech recognition system, CMU Sphinx, which is similar to commercially available speech recognition systems for dictation programs, he said.
Commercial programs to recognize speech are available mainly for major languages, so the Carnegie Mellon team developed a Croatian-English dictionary with 5,000 to 10,000 words in English and the same number in Croatian, a size the laptop can easily handle.
Other problems awaited the team. Just as dictation programs are trained to learn the particular cadences of their owners -- that is, to recognize the way each person pronounces words -- this program had to be trained to recognize the cadences of the chaplains.
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