2010 Volume 34 Issue 3 Pages 260-266
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.
