Although drivers rely on horns to warn them of approaching trains at railroad crossings, the level of horn sounds necessary for detection has not yet been established. This study seeks to obtain baseline measures of the auditory component of the motorist's detection task. Horn sounds recorded in three test vehicles were presented to 20 normal-hearing listeners in quiet and in four types of vehicle interior noise: engine idling, ventilation fan off; engine idling, fan on; vehicle moving at 30 mph, fan off; and vehicle moving at 30 mph, fan on. Thresholds of the horn sounds were determined by an adaptive procedure. Mean thresholds were lowest in quiet (1.8-4.4 dBA) and highest for the 30-mph, fan-on condition (49.7-58.4 dBA). Mean horn thresholds for all 12 noise conditions were more than 10 dB below the overall level of the vehicle interior noise. The data suggests that the lower limit of signal-to-noise ratios required for the detection of train horns is about -10 dB.
Samenvatting