Field experiment on ground-to-ground sound propagation from a directional source

When predicting sound propagation in long distance, meteorological effects resulting from wind and temperature should be taken into consideration. Regarding this problem, many studies have been carried out by field measurements, numerical analyses and physical experiments. To predict and assess traffic noise by vehicles, trains and aircrafts, the sound sources are roughly modeled as omnidirectional. In reality, however, the sources have their inherent directivities according to their shapes, and the directivity can affects noise propagation characteristics as well as the meteorological effects. In this study, a field experiment on ground-to-ground long distance sound propagation using an omnidirectional loudspeaker and two types of directional loudspeakers were conducted at a flat field which approximately satisfied hemi-free field condition. To examine the relationship between the directivity effects and the meteorological effects, sound propagation characteristics by an omnidirectional loudspeaker and those by directional loudspeakers were compared. In addition, sound propagation by the omnidirectional point source was analyzed using Crank-Nicholson Parabolic Equation analyses and the experimental results were validated. Consequently, it was confirmed that sound propagation from the directional sources showed the same trend for excess attenuation characteristics as that from the omnidirectional source by considering its directional characteristics.