Evaluation of an experimental central warning system with a synthesized voice component.

The experiment monitored the use of an experimental central warning system by experienced pilots. The warning system incorporated audio warnings, voice messages, and panel legends. The voice messages were produced by a Votrax synthesizer. Warning responses were assessed during a realistic flying task. Audio warnings produced significantly faster responses than panel legends or voice messages. Voice messages and audio warnings had a greater distracting effect on subjects' responses than panel legends. Workload level did not affect response to either the voice or audio warnings but responses to panel legends did lengthen significantly at high levels of workload. The Votrax voice messages were disliked by the pilots who adopted a strategy of cross-referring to panel legends upon hearing the attention-getting sound which preceded the voice messages because they had difficulty understanding the Votrax messages. The results suggest that Votrax voice messages may only augment the noise level of the flight deck and could effectively be replaced with an attention-getting sound and panel legend. It is also suggested that crew response to synthetic voice messages which can be understood on first presentation will be more positive than their response to Votrax messages.

The speed of response to synthesized voice messages.

The experiment evaluates the effectiveness of synthesized cockpit voice warning messages using measures of reaction time (RT). Research has shown that voice messages are comparable to audio warnings and that synthesized voice messages are easily recognizable at low signal to noise ratios. This study evaluates synthesized voice messages are easily recognizable at low signal to noise ratios. This study evaluates synthesized voice messages by observing their performance in combination with auditory and visual indicators. Four different warning arrangements were used of which three had a Votrax voice component. The four warning systems represented future possible warning combinations for transport aircraft. Subjects had to deal with simulated emergencies whilst performing a psychomotor tracking task and monitoring ATC messages. Thirty commercial pilots took part in the study. Overall the four warning systems were equally effective in terms of RT. However, voice messages had significantly slower RTs than audio warnings. Voice messages and illuminated legends caused significantly less disruption of ATC monitoring than audio warnings. Pilots also consistently cross-checked voice and audio inputs with visual indicators. It is suggested that the proliferation of cockpit voice inputs should be avoided until human factor evaluations of simpler but equally effective warning systems have been completed.