The authors have developed a tool for presenting a sonic environment with the information of the sound sources as well as the sound levels. The sonic environment is expressed as a two-dimensional graphic chart named ‹Sound source×Sound level› Time-component Matrix Chart (abbreviated as TM Chart). In this study, we investigate the availability of the TM Chart by measuring the changes of sonic environments in a social experiment of a transit mall conducted in Kyoto. The conventional noise indices, i.e. LAeq, LAmax , LAmin and percentile sound levels detected the changes of the sonic environments at the only limited measuring points. The TM Chart, however, showed more detailed and visual information on the changes of the sonic environments with the percentage time of the sound sources and the percentage time of the sound levels.
In Japan, the Building Standards Law was revised in 2003 and installation of ventilation systems working for 24 hours was obliged to prevent sick building syndrome. Under such a situation, it is required to develop the ventilation equipment with high sound insulation performance especially for residential buildings in noisy areas. In this study, therefore, a duct-type ventilation system with high sound insulation equipped to glass sliding windows has been developed, in which two types of acoustical filters, resonators with slit-shaped apertures for lower frequencies and series of thin panels for higher frequencies, are combined. The sound insulation performance of the duct-type ventilation system with the designed array of acoustical filters was examined by performing full-scale model experiment using sound intensity measurement technique. As a result, sound insulation performance of the ventilation system was improved in a broad band frequency range.
The practical method of ASJ RTN-Model 2008 is widely used in Japan to predict road traffic noise. In this method, the sound propagation is not calculated for each frequency but for A-weighted sound level directly. The accuracy of the prediction would decrease if there exist multiple reflections or diffractions where the frequency characteristics of road traffic noise change remarkably. This study focused on the noise from a tunnel entrance since the sounds reflect multiply inside the tunnel. A calculation model was developed for the prediction of the sound propagation from a tunnel entrance for each octave band, which modifies some other issues in the calculation, i.e., the assumption of an imaginary sound source for evaluating propagation of direct sound, and the assumption of semi-infinite noise barrier for evaluating diffraction of direct sound. As a solution, an imaginary plane sound source having directivity was placed on the tunnel entrance.