3.1. Effect of 10lg Du
p
In the FHWA model [Eq. (2)], 10lgðDu
p Þ represents the revision
item for the finite length of road. If this item was neglected, the
application of the FHWA model would be limited to some extent,
such as in predicting the traffic noise sound level of a receiving
point which is located at the tunnel portal of a highway. As shown
in Fig. 2, when predicting the traffic noise sound level of the
receiving point C using Eq. (6) with Ni = 1 vehicle per hour,
Vi = 120 1000 m/h and D = 30m (2D0), the 1 h equivalent
continuous sound pressure level was