Appendix F: Computing Maximum Noise Level for a Single Train Passby
F-1
APPENDIX F. COMPUTING MAXIMUM NOISE LEVEL (Lmax)
FOR A SINGLE TRAIN PASSBY
This appendix provides procedures for the computation of Lmax for a single train passby, for those readers
desiring such procedures. Table F-1 contains the equations to compute Lmax. The procedure is
summarized as follows.
•
Collect the following input information:
o SELref's from Chapter 6, specific to both the locomotive type and car type of the train
o Nlocos, the number of locomotives in the train
o Ncars, the number of cars in the train
o Llocos, the total length of the train's locomotive(s), in feet (or Nlocos(unit length)
o Lcars, the total length of the train's set of rail car(s), in feet (or Ncars(unit length)
o S, the train speed, in miles per hour
o D, the closest distance between the receiver of interest and the train, in feet
•
Compute Lmax,locos from the locomotive(s) using the first equation in Table F-1.
•
Compute Lmax,cars from the rail car(s) using the second equation in Table F-1.
•
Choose the larger of the two Lmax's as the Lmax for the total train passby.
F-2
Transit Noise and Vibration Impact Assessment
Table F-1. Conversion to Lmax at the Receiver, for a Single Train Passby
Equation
Source
Locomotives
⎛ L⎞
⎛ S ⎞
L max,lo cos = SELlo cos + 10 log⎜ ⎟ − 10 log⎜ ⎟ + 10 log(2 ∝) − 3.3
⎝ 50 ⎠
⎝ 50 ⎠
Rail Cars
⎛ S ⎞
⎛ L⎞
L max,cars = SELcars + 10 log⎜ ⎟ − 10 log⎜ ⎟ + 10 log[2 ∝ + sin(2 ∝)] − 3.3
⎝ 50 ⎠
⎝ 50 ⎠
Total Train
L max,total = max L max,lo cos orLmax,cars
[
]
D
L
S
= closest distance between receiver and source, in feet
= total length of measured group of locomotive(s) or rail car(s), in feet
= vehicle speed, in miles per hour
∝
⎛ L ⎞
= arctan ⎜
⎟, in radians
⎝ 2D ⎠
Example F-1. Computation of Lmax for Train Passby
A commuter train will pass by a receiver of interest and its Lmax is desired. For this train, the following
conditions apply:
SELref =
=
Nlocos =
Ncars =
S
=
D
=
92 dB for locomotives and
82 dB for rail cars
1
6
43 miles per hour
125 feet.
The locomotive and rail cars each have a unit length of 70 feet. Therefore,
Llocos =
70 feet
420 feet
Lcars =
Using the equations in Table F-1,
∝ lo cos =
0.27
∝ cars
=
1.03
and the resulting Lmax's are as follows:
84 dBA
Lmax,locos =
Lmax,cars =
74 dBA
84 dBA.
Lmax,total =
End of Example F-1