WIDE-BAND MEASUREMENTS AND ANALYSIS OF SOUNDSCAPE OF NORTHERN AREA

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(1) Measurements of SoundscapeWe have measured sound of the city (Sapporo) and in the mountains (Haruka-yama) in wide frequency range of 0-20kHz, and analyzed their power spectrums and characteristics of level changes. As a results of the analysis, the spectrum of natural sound has a peak level at the frequency about 1kHz, and decreasing gradually with frequency up to 7-8kHz, and remained almost unchanged above that frequency rage. The spectrum of the city, on the other hand, is decreasing with frequency monotonously, and its level of the frequency above 15kHz or so is very small.(2) Development of 3-D Ray-tracing Program of SoundWe developed three dimensional ray-tracing program for acoustic wave. For calculation of the propagation path of acoustic energy, we have to specify an atmospheric model such as temperature profiles, wind velocity models, sound speed models, terrain models, and so on. The program traces the acoustic ray path by numerically integrating Hamilton's equations, which are a differential expression of Fermat's principle.(3) Map of Well-known Sound in HokkaidoWe didn't start on making the map of famous sound scape in Hokkaido. However, Nippon Hoso Kyoukai (NHK) begun to invite a local famous sound and a spiritual sound over national levels.