2.C. Definition of Primary Project Noise K= flow noise constant (K = 6 for vehicles with
Sources turbochargers)
The Project was assumed to operate during day- l
exh
= length of exhaust pipe (m)
time business hours that change seasonally. During B = fuel compression correction constant (-3 for
any one hour of operation, the Project is expected to unleaded fuel)
have a combination of mobile and stationary sound C = cylinder arrangement constant ( -1 for
sources as follows: ‘V’-type engines)
• Sports cars (up to 750HP each), motorcycles
Further, each of the three vehicle types has unique
(up to 150HP each), or karts (up to 40HP each)
characteristics as follows:
on the main track;
• Idling vehicles of like varieties in the Pit Area
and garages; and • Sports car – turbocharger, 3m tailpipe, medium
• Karts on the kart track. insertion loss (IL) low pressure drop muffler,
and a 1m intake duct.
Octave band sound power levels of each source
• Motorcycle – no turbocharger, 1.5m tailpipe,
are provided in Table 2, Noise Model Parameters.
Table 2. Noise Model Parameters
Sound Power Level (SWL)
Project Type of
at Octave Band Center Frequency (Hz)
Component
A-Weighted
Source
31.5 63 125 250 500 1000 2000 4000 8000
Moving
Sports Car
point 134 121 122 121 118 119 118 115 108 124
(up to 750 HP)
source
Moving
Motorcycle
point 134 120 121 120 115 114 112 109 101 119
(up to 150 HP)
source
Moving
Kart
point 135 131 137 133 125 122 117 111 103 129
(up to 40 HP)
source
Pit Area Idling Area
117 109 102 83 68 63 58 53 48 88
Vehicle source
The important component sound power sources medium insertion loss (IL) low pressure drop
for these types of sports car and similar internal com- muffler, and a 0.5m intake duct.
bustion engine platforms are the engine exhaust (L
w,
• Kart -- no turbocharger, 0.5m tailpipe, no muf-
exh
), the engine casing (L
w, cas
) and the air inlet (L
w,
fler, no intake duct, and exposed engine (i.e.,
inl
), which are calculated using the equations below:
3
+6 dB penalty).
For engines with no turbocharger, inlet noise is
L
w, exh
= 120 + 10 * Log(P) – K – l
exh
/ 1.2
negligible in comparison to the casing and exhaust.
(1)
Turbocharged engines follow the math expression
above and are subject to octave band corrections as
L
w, cas
= 93 + 10 * Log(P) + B + C
the casing and exhaust levels are. These three indi-
(2)
cated component sources are logarithmically summed
(L
w, vehicle
), so that each moving vehicle is a point
L
w, inl
= 95 + 5 * Log(P) – l
exh
/ 1.8
source and generates a sound power calculated by the
(3)
following equation:

These equations incorporate the following param- L
w, driving
= L
w, vehicle
+ 10 * LOG(Q) - 10 *
eters: LOG(V) – 30; (4)
where L
w, driving
is the sound power level (PWL, in
P = Power (kW)
dB) of a given vehicle driving around a track; Q is the
22 • Alumni Arsenal | November 2009 The Official Magazine of the NSBE Alumni Extension
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