To design educational environment in nursery institutions focused on sound environment, we report the result of sound environment investigation in the kindergarten and experimentally design focused on acoustic characteristics. To understand the environment from children's viewpoint that is different from adult's one and do feedback these knowledge to the design, we examine the design focused on children's hearing height and their behavioral pattern. Children's hearing height is greatly influenced by sound reflected from floor side and furniture side; therefore the experimental acoustic design using two kinds of carpets is done. The change of the acoustical characteristics is shown as a difference of reverberation time that the sound absorption of carpet is especially remarkable in 1-4kHz frequency bands. When the carpet is laid at the activity scene in the kindergarten, the effect of the sound absorption by carpet is little. Meanwhile, in the free activity scene that children act voluntarily, relations between children and the environment, specifically how to use the nursery room and their behavior themselves change greatly. Although there are few children who stay and act for a long time in nursery room at normal situation, we observed that the room is actively used as a place of make-believe play when the carpet A with short wool is laid and dynamic action such as running about or jumping when the carpet B with long wool is laid. As a result, the characteristics of the actual sound change greatly by the occurring sound caused by the behavioural change more than the acoustic characteristics.