Design of Natural Warning Sounds
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The goal of this research is increased safety and human performance in aviation. Human errors are often consequences of actions brought about by poor design. The pilot communicates with the aircraft system through an interface in cockpit. In an alerting situation this interface includes an auditory alerting system. Pilots complain that they may be both disturbed and annoyed of alerts, which may affect performance, especially in non-normal situations when the mental workload is high. This research is based on theories in human factors /ergonomics and cognitive engineering with the assumption that improved human performance within a system increase safety. Cognitive engineering is a design philosophy for reducing the effort required by cognitive functions by changing the technical interface, which may lead to improved performance. Knowledge of human abilities and limitations and multidisciplinary interrelated theories between humans, sounds and warnings are integrated into this research. Several methods are included, such as literature studies, field studies, controlled experiments and simulations with pilots. This research provides design requirements for sounds appropriate as auditory alerts, defined as Natural Warning Sounds. These sounds either have a natural meaning within the user's context, or are compatible with the human's natural auditory information process, or both, they are also pleasant to listen to (not annoying), easy to learn and clearly audible. In an experimental study associability of different sounds were compared. Associability is the required effort to associate sounds to their assigned alert function meaning. The more associable a sound is it requires less effort and fewer cognitive resources. The study shows that auditory icons and animal sounds were more associable than conventional alerts! In another listening study the method of Soundimagery was used to develop soundimages. A soundimage is a sound, which by its acoustics characteristics has a particular meaning to someone without prior training in a certain context. Soundimages were successfully developed, however it may be difficult to come up with sound candidates for functions that lack sound or are not associated to a particular sound. In a simulation study different presentation formats were compared. The results show that auditory systems should have cancellation capabilities and avoid continuously repeated alerts. This research brings related theories closer to practice and demonstrates methods that will allow designers, together with the users of the system, to apply them in their own system design.