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.