WHAT'S NEXT; Unearthing Information in an Avalanche of Voice Mail
By YUDHIJIT BHATTACHARJEE
Published: April 25, 2002
OF the many tasks that await after a vacation, one of the most tedious is listening to a long string of voice-mail messages and sorting out the urgent ones from the hey-what's-going-on variety. The only way to do this is to play every message, at least in part, with pencil in hand to jot down callback numbers and other information.
It need not be such a chore, say researchers at AT&T Labs in Florham Park, N.J., who have built a system that allows browsing through voice mail as one would e-mail. The system, called ScanMail, uses speech recognition technology to transcribe voice-mail messages so that they can be searched on a computer by keyword, the sender's name or a phone number. When a relevant part of a message is located, the user can play that part of the voice mail by double-clicking on the selected text.
The inventors of the system say that it could become an important addition to the communications systems of many businesses, especially corporations whose employees routinely have to deal with overflowing voice-mail boxes. ScanMail would be particularly useful to corporate executives and marketing professionals who spend much of their time holed up in meetings away from their offices.
''Many people in that situation spend their coffee breaks calling their offices, trying to find out if they have any urgent messages waiting,'' said Dr. Julia Hirschberg, one of the researchers who developed the AT&T system. With ScanMail, such people would be able to call up their voice mail on their laptops or hand-held organizers without leaving the conference room.
The system consists of servers connected to a hub. It receives voice mail in the form of audio files from a standard messaging system. The files are routed through the hub to ScanMail's automated speech recognition server, a powerful computer trained to match thousands of verbal sounds to written words. (The researchers programmed the computer by entering 100 hours of recorded voice-mail messages into the computer's database along with the manually transcribed text of each message.)
The speech recognizer takes about 12 times longer than the duration of a given message to produce a transcript. Both the transcript and the sound file of the message can be downloaded on any PC linked to the hub. Users receive their messages on their PC's as e-mail with audio-file attachments.
When a user runs a search for some specific content -- say, for messages containing the word ''Geneva'' -- the system processes the request by using servers that handle information extraction and retrieval.
The system's performance rests on the quality of its speech recognition -- a technology that researchers acknowledge is still far from perfect. Given the wide variations in accent, pace and clarity in human speech, the best speech recognition systems get a significant percentage of words wrong.
Dr. Michiel Bacchiani, an AT&T researcher who worked on ScanMail's speech recognition component, said that although the error rate of the system was not inconsiderable, about 27 percent, it was good enough for meaningful searching and browsing of the voice-mail content.
''It gives the system enough grip to find a particular message within a body of messages,'' Dr. Bacchiani said. ''Even if a transcript is imperfect, it gives the user an approximate idea of what was said.''
Other researchers are developing systems capable of searching audio content on the Internet. Pedro Moreno and colleagues at Compaq's Cambridge Research Laboratory in Massachusetts have designed a system called SpeechBot that trolls the Web for audio files, downloads them on computers at the Compaq lab and transcribes them. Using a network of 90 machines, the system has cranked out transcripts for more than 14,000 hours of Web audio, mainly from sites run by by media companies.
SpeechBot, which can be sampled at no charge on the Internet (speechbot.research .compaq.com), has indexed all of this audio content. A text-based query punched into its search engine yields a list of audio files that contain the words in the query. When the user selects a file, a box on the screen displays the relevant transcribed section of the audio file. Like ScanMail, SpeechBot can play a selected audio extract.
Depending on the nature of the audio, SpeechBot's transcription can be sprinkled with errors; the worst transcripts border on gibberish. Dr. Moreno said that despite the high error rate, the system could still provide the approximate location of specific audio content that users might be seeking.
Researchers envision that systems like SpeechBot will be used as search tools for audio and video archives on the Internet.
Another potential application is intelligence-gathering. There is so much audio and video broadcast around the world that intelligence agencies find it impossible to analyze most of it, Dr. Moreno said. ''Even with errors,'' he said, ''searches based on speech recognition could save analysts valuable time.''
But if audio searching is to have wider applications, said John Makhoul, a researcher in speech and language processing at BBN Technologies in Cambridge, the technology needs to become more precise. A system for searching voice mail received at home, for instance, is likely to require finer speech-recognition capabilities than a system designed for the office. ''Business voice mail tends to be much more formal and less conversational than other voice mail,'' Dr. Makhoul said.
David Nahamoo, manager of the human language technologies division at I.B.M. Research, said that audio search technology might one day be heavily used in the call-center business, where hundreds of messages have to be handled by human listeners every day. Running text-based searches of transcripts of recorded calls could help such centers improve efficiency, he said.
Drawing (Mary Ann Smith)