The purpose of these reports (report No.3-5) is to clarify the structure of the wind flow around buildings in urban area. In report No.4, the results of the observation of the wind veloccity within the housing estates in which one-storied houses are regularly distributed in large area are reported. Then, in report No.5, the results of the observation of the wind velocity around tall buildings in urban area are reported. In this report, No.3, Authors mentioned about the way of analysis on fluctuation of the wind velocity, and examined the dynamic responce characteristics of instruments, and also discussed their relations to the observation time and the interval of sumpling time. That is (1) Authors indicated a method of linearized of output of H.W. Anemometer (as against the wind velocity). Therefore the wind velocity was put on data-recorder through the use of a way of above-mentioned, and authors showed the way of analysis of frequency from the use of the play-back speed what is more higher than regular speed. In this way, for instance, analysis of freqency range from 0.05Hz. to 25Hz. should be possible. Authors showed the method of degigtal analysis which were used computation in this report, discussed influence of the data total (N) and lag number (H) on results of the Analysis. (2) Authors inspected the dynamic responce characteristics of the wind velocity measuring equipments H.W. Anemometer, Thermo-Couple Anemometer, Three Cup Anemometer and their recorders and concluded that the minimum interval of sampling time should be from 1 to 4 sec. (3) In result, authors have gained that observation time should be over about 30 min., and have got at the conclusion that the number of data should be desirable over 400 pieces.
