WIDE-BAND MEASUREMENTS AND ANALYSIS OF SOUNDSCAPE OF NORTHERN AREA

(1)声景观测量我们在0-20 kHz的宽频范围内测量了城市(札幌)和山区(Haruka-yama)的声音，并分析了它们的功率谱和电平变化特征。分析结果表明，自然声的频谱在1 kHz左右有一个峰值，在7-8 kHz范围内随频率的增加而逐渐减小，在此频率范围内基本保持不变。另一方面，城市的频谱随频率单调递减，其频率在15 kHz左右的水平很小。(2)声三维射线追踪程序的开发我们开发了声波三维射线追踪程序。为了计算声能的传播路径，我们必须指定一个大气模型，如温度分布、风速模型、声速模型、地形模型等。该程序通过数值积分哈密尔顿方程来跟踪声线路径，哈密尔顿方程是费马原理的微分表达式。(3)北海道著名声音地图我们并不是从制作北海道著名声音景观地图开始的。然而，日本Hoso Kyoukai(NHK)开始邀请地方名声和全国水平的精神声音。

(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.