Long-term Measurements of Sound Refraction Paths over Residential Areas using Emergency Public Address Systems

In Japan, there are many outdoor emergency public address systems for disaster prevention, which utilize a radio system including a master station installed in a local government office and a plurality of slave stations in a town. The outdoor loudspeaker slave stations, each about 500 m apart, produce the same contents at a prescribed time every day for the purposes of maintenance. Long-term measurements of the test sounds were carried out in several residential areas in Tokyo. The sound propagation times for the plural slave stations were calculated from cross correlations between radio wave signals from a master station and sound pressure signals at several monitoring points. And sound refraction paths over two stories houses in residential areas were estimated. The results under many meteorological conditions were compared with calculations by the Harmonoise prediction model.