Auditory Localization of Backup Alarms: The Effects of Alarm Mounting Location 2011-01-0086

Sound localization of a backup alarm is important in situations when vehicles are reversing. Previous work has demonstrated the effects of ambient noise level and the spectral content of the backup alarm on localization. In the current study, we investigate the effects of backup alarm mounting location on localization performance. To address this question, we asked blindfolded listeners to localize backup alarms installed in positions that provided either direct (e.g., installed on the outer rear aspect of the vehicle) or indirect (e.g., installed within the inner frame rails of the vehicle) sound propagation paths to the listener. Additionally, we explored the effects of ambient noise level and the direction of origin of the alarm (behind, in front of, or to the left or right of the listener), and the interactions among all three factors (alarm location, ambient noise, and alarm direction relative to the listener). Localization performance was examined in terms of percent correct localization, as well as percent front-back confusion errors. When the alarm stimuli were presented in front, the alarm that was mounted directly in front of the listener -- providing a direct path to the listener --produced more correct localizations than the other alarms. This direct-path alarm also resulted in the least front-back confusions overall. However, when the alarm stimuli were presented behind the listener, the alarm mounted at the top of the rear of the truck --providing a direct but elevated path to the listener -- produced the worst performance and the most front-back confusion errors. An important factor affecting listeners' localization performance was the orientation of the listener relative to the direction from which the alarm stimuli originated. When the alarm was to the right or left of the listener, all alarm mounting locations produced equally good performance and no front-back confusions. Alarms originating from behind the listener, however, generally produced the worst performance, and the most front-back confusions, for the majority of the alarm mounting locations.