Railway bonus and aircraft malus for different directions of the sound source?

Even for same LAeq, noise immissions from different types of traffic noise elicit not always the same loudness and annoyance. Frequently, railway noise is perceived as less annoying than road traffic noise (railway bonus), whereas aircraft noise can be perceived as more annoying than road traffic noise (aircraft malus). As one possible reason for the aircraft malus in addition to differences in spectral distribution and temporal structure sometimes the hypothesis is put forward that sounds which come from above a person are perceived as particularly dangerous and annoying. In order to challenge this hypothesis, psychoacoustic experiments were performed in which the same immissions of equal LAeq from railway noise, road traffic noise, and aircraft noise were presented by loudspeakers in front of versus above the subjects. They had to rate the overall loudness of the noise immissions by category scaling, magnitude estimation, and line length. Results are presented in which the magnitude of bonus or malus is given as a function of the direction of the sound sources. For presentation in front of the subjects, both railway bonus and aircraft malus were found. However, for “natural" situations like road traffic noise from front and aircraft noise from above, no aircraft malus showed up.