This paper intends to report on investigations made on effects of street noise upon the learning of pupils in school rooms. 4. 357 pupils among 6 primary, 3 junior and 2 senior schools in Osaka City were selected. The situations of these schools, in which the subjects were learning, were noisy. The following investigations were performed: (1) The psychic and somatic response of pupils on the noise caused by traffic, whistle etc. by means of questionnaire method. (2) Kraepelin's tests and syllable articulation tests in noisy and quiet school rooms. The following results were obtained: (1) The sound levels encountered in noisy school rooms (91 rooms) ranged 40-65 phons and in about one quarter of these rooms, the levels were 55 phons or higher while the sound levels in quiet school rooms (investigated as control) ranged 40-45 phons. (2) Among the replies by the subjects who studied in noisy school rooms with the sound level higher than 55 phons, more than 50 % filled out "Yes (measuring, difficulty)" regarding to the items concerned with emotion and perception of speech while same answer was given by 31 % of the subjects regarding to mental works and 24 % regarding to physical conditions. (3) The statistical study of Kraepelin's tests revealed that there were no significant differences in the work amount, the percentage of errors the percentage of rest efficiency between the tests in noisy and quiet school rooms. (4) In noisy school rooms, with noise level higher than 55 phons, articulation of syllable decreased especially at the rear seats. (5) The noise level in school rooms, which are exposed to street noise, seems necessary to be lower than 55 phons for satisfactory learning.
