A survey was conducted to gather data for an assessment of the vocal noise level from children playing in nursery schools or other similar facilities. Ten nursery schools were surveyed; 5 locations in Setagaya Ward, Tokyo and 5 in Hachinohe, Aomori Prefecture. The surveys considered two cases: the noise levels while the children were playing in the yard, and those while they were playing inside. Measurements were taken over 10-minute intervals and the variables analyzed were equivalent continuous A-weighted sound pressure level ( called equivalent continuous noise level ), maximum noise level, percentile noise level, and frequency (1/1 and 1/3 octave bands). Additionally, at the first nursery school surveyed, a continuous measurement of the noise level was conducted for 24 hours to examine the conditions of measurements and the length of the analysis period.
The noise level was found to be approximately 20 dB higher while the children were playing in the yard or in the pool than during other times of day, and that was about 30 dB louder than at night. In the nursery schools where the measurements were taken, the noise levels were also about 5 to 7 dB higher while the children were entering in the morning, which was not a dramatic difference.
The equivalent continuous noise level measured 10 m from the center of a group of children playing in the nursery school yard was about 62 dB when there were 10 individuals and 74 dB when there were 100 individuals. However, it was possible for the noise to momentarily reach levels over 90 dB. The mean level of the vocal noise also increased by about 10 dB during music classes and when a microphone was being used.
The frequency analysis of vocal noise from children indicated peaks of around 1000 Hz and 2000 Hz. There were linear decreases from these peaks at other frequencies. These values were higher than the pitches observed from conversations involving only adults.
The effectiveness of a noise barrier installed within the nursery school grounds was estimated using the above results. Four cases were considered, where the height of the wall was varied from 2.0 m to 3.5 m. The wall was estimated to reduce the noise by 15 － 20 dB, which was considered to be sufficiently effective.
