No abstract

Examples of poor heavy-weight floor impact sound performance of pure framed structures with reinforced concrete were observed relative to the floor slab thickness. To investigate the cause of the poor performance, the floor vibration characteristics of several examples of actual pure framed structures were measured during heavy-weight impact. As a result, the floor vibration characteristics of the displacement of the girders and coupled vibration of the girders and floor slabs not seen in conventional floor structures surrounded by girders with reinforced concrete walls were observed. The propagation of the vibration of the floor slab was observed in more than the range surrounded by girders and in the next slab beyond the girders owing to the vibration of the girder itself. That these physical phenomena can be evaluated using a numerical calculation method was confirmed, and the vibration of the girder itself and the actual vibration range when the floor slab is subjected to heavyweight impact must be considered to accurately predict the heavy-weight floor impact sound performance.

The road traffic noise prediction model ''ASJ RTN-Model,'' which has been developing by the Research Committee in the Acoustical Society of Japan, is used widely in environmental impact assessment in Japan. In the latest model, ASJ RTN-Model 2018, several coefficients of the calculation equation for the A-weighted sound power level of road vehicles were updated. In European countries as well, various prediction models such as Nord, Harmonoise, and CNOSSOS-EU have been published. Since 2018, the specific noise emission, which can be incorporated into CNOSSOS-EU, was proposed in several countries: CNOSSOS-NL, -FR, and sonROAD. Also, the emission values in CNOSSOS-EU were replaced in 2021. Thus, the values of noise emission and its frequency characteristics were compared between these prediction models using the immission values calculated considering the effects of a barrier and the ground surface. The results demonstrated that a valid relationship exists between the emission values in ASJ RTN-Model 2018 and those in European models. Additionally, in the prediction assuming a reflective ground such as in urban areas, the differences in frequency characteristics of noise emission between the models will be negligible.

Flexible wooden boards with new sound absorption characteristics have been developed to improve the indoor acoustic environment of buildings. These sound absorption characteristics, achieved with a Helmholtz resonator, vary depending on the cross-sectional shape and surface shape of the boards. Also, the sound absorption performance is confirmed in an actual building. The results will lead to the development of sound-absorbing wooden as interior materials and also promote wooden interiors of public buildings.