Speech Recognition - Important Concepts in Signal Processing, Image Processing and Data Compression - page 42

Military
High-performance fighter aircraft
Substantial efforts have been devoted in the last decade to the test and evaluation of
speech recognition in fighter aircraft. Of particular note is the U.S. program in speech
recognition for the Advanced Fighter Technology Integration (AFTI)/F-16 aircraft (F-16
VISTA), and a program in France installing speech recognition systems on Mirage
aircraft, and also programs in the UK dealing with a variety of aircraft platforms. In these
programs, speech recognizers have been operated successfully in fighter aircraft, with
applications including: setting radio frequencies, commanding an autopilot system,
setting steer-point coordinates and weapons release parameters, and controlling flight
displays.
Working with Swedish pilots flying in the JAS-39 Gripen cockpit, Englund (2004) found
recognition deteriorated with increasing G-loads. It was also concluded that adaptation
greatly improved the results in all cases and introducing models for breathing was shown
to improve recognition scores significantly. Contrary to what might be expected, no
effects of the broken English of the speakers were found. It was evident that spontaneous
speech caused problems for the recognizer, as could be expected. A restricted vocabulary,
and above all, a proper syntax, could thus be expected to improve recognition accuracy
substantially.
The Eurofighter Typhoon currently in service with the UK RAF employs a speaker-
dependent system, i.e. it requires each pilot to create a template. The system is not used
for any safety critical or weapon critical tasks, such as weapon release or lowering of the
undercarriage, but is used for a wide range of other cockpit functions. Voice commands
are confirmed by visual and/or aural feedback. The system is seen as a major design
feature in the reduction of pilot workload, and even allows the pilot to assign targets to
himself with two simple voice commands or to any of his wingmen with only five
commands.
Speaker independent systems are also being developed and are in testing for The F35
Lightning II (JSF) and the Aermacchi M346 lead in fighter trainer. These systems have
produced word accuracies in excess of 98%.
Helicopters
The problems of achieving high recognition accuracy under stress and noise pertain
strongly to the helicopter environment as well as to the fighter environment. The acoustic
noise problem is actually more severe in the helicopter environment, not only because of
the high noise levels but also because the helicopter pilot generally does not wear a
facemask, which would reduce acoustic noise in the microphone. Substantial test and
evaluation programs have been carried out in the past decade in speech recognition
systems applications in helicopters, notably by the U.S. Army Avionics Research and
Development Activity (AVRADA) and by the Royal Aerospace Establishment (RAE) in