APPLICATION STORY

 Voice Monitoring System for Airline Pilots.



Chaos theory tells pilots when to take a break. AIRLINE pilots and air traffic controllers who are too tired to work safely could soon be identified automatically, thanks to a Japanese monitoring system that analyses voice patterns for signs of fatigue. "Our system is able to detect tiredness in test subjects 10 to 20 minutes before the subjects themselves notice it," says Kakuichi Shiomi, chief researcher at the Electronic Navigation Research Institute near Tokyo, which developed the system.
Human error currently accounts for around 80 per cent of all air accidents worldwide. "Crew fatigue is a very real problem, especially on long-haul flights crossing many time zones," says Shiomi. Called a fatigue and drowsiness predictor, the system uses the mathematics of chaos theory to compare changes in the voices of wide-awake, alert people with those of fatigued people. The change is known to be related to a drop in blood pressure when people are tired-but it is very subtle. So Shiomi's team at ENRI, a division of the Japanese Ministry of Transport, had to come up with a way of analysing speech that brings these small changes into sharp relief. The system takes advantage of the fact that many biological signals, including heartbeat and blood pressure-have a fractal structure. Like a coastline or a lightning flash, the pattern of the signal is equally jagged no matter how closely you zoom in on it. But with voice signals there's one important difference: the fractal structure changes when the speaker is fatigued. The changes are hard to spot by simply watching the voice waveform, so the ENRI team wrote software that converts a voice signal's fractal structure into a graphical pattern that magnifies subtle, small changes. Alert voice pattern has a well-ordered trace.
Drowsy voice pattern is chaotic and spiky.
To test their system, the researchers processed recordings of subjects as they concentrated on reading or doing maths. When wide awake and alert, their voice fractal graphics are well defined (see Diagram). But after 20 to 30 minutes of reading, they become noticeably more jagged. In a cockpit or air traffic control centre, an image processor could recognise the fatigue pattern and raise the alarm when staff are becoming fatigued, signalling that it's time for a more alert colleague to take over. Tests of the fatigue predictor are now planned on real pilots and air traffic controllers. If these are successful, Shiomi envisages using the system on other transport systems, such as oil tankers, where the verbal commands of drivers and pilots can be monitored. _______________________________________________________ From an article in the New Scientist by Peter Hadfield and Paul Marks Web: www.newscientist.com December 2000
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