WIDE-BAND MEASUREMENTS AND ANALYSIS OF SOUNDSCAPE OF NORTHERN AREA

我们测量了城市（札幌）和山区（春山）在0-20kHz宽频率范围内的声音，并分析了它们的功率谱和电平变化特征。分析结果表明，自然声音的频谱在1kHz左右有一个峰值水平，在7-8kHz范围内逐渐下降，在该频率范围以上基本保持不变。而城市的频谱是随频率单调递减的，其15kHz以上的频率水平非常小。(2) sound3维光线追踪程序的开发我们开发了声波的3维光线追踪程序。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。该程序通过对费马原理的微分表达式——汉密尔顿方程进行数值积分来追踪声波路径。(3)北海道著名声景图我们并没有开始制作北海道著名声景图。然而，日本放送协会（NHK）开始在全国范围内邀请当地的名声和精神之声。

(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.