Eq. (7) is the accurate expression of Leq(20 s) model derived
from the FHWA model, which was built based on a precise
mathematical derivation [5,13]. Du and 2arctanð20Vi=7200D0Þ in
Eq. (7) do not represent the same angle. These two items cannot
be cancelled out in some situations, which will be discussed in
the latter parts of this paper.
3. Discussion of Leq(20 s) model
A mathematical model for calculating the hourly equivalent
sound level based on the basic vehicular noise Leq(20 s) was
proposed by Pamanikabud [12] and was called the Leq(20 s) model.
The expression of the Leq(20 s) model was