799 

Federal Aviation Administration, DOT 

Pt. 36, App. A 

(1) XY represents the portion of the meas-

ured flight path that includes the noise time 
history relevant to the calculation of flyover 
and approach EPNL; X

r

Y

r

represents the cor-

responding portion of the reference flight 
path. 

(2) Q represents the airplane’s position on 

the measured flight path at which the noise 
was emitted and observed as PNLTM at the 
noise measuring station K. Q

r

is the cor-

responding position on the reference flight 
path, and K

r

the reference measuring station. 

QK and Q

r

K

r

are, respectively, the measured 

and reference noise propagation paths, Q

r

 

being determined from the assumption that 
QK and Q

r

K

r

form the same angle 

q 

with their 

respective flight paths. 

(b) The portions of the test flight path and 

the reference flight path described in para-
graph (b)(1) and (2), and illustrated in Figure 
A36–7(a) and (b), include the noise time his-
tory that is relevant to the calculation of 
lateral EPNL. 

(1) In figure A36–7(a), XY represents the 

portion of the measured flight path that in-
cludes the noise time history that is relevant 
to the calculation of lateral EPNL; in figure 
A36–7(b), X

r

Y

r

represents the corresponding 

portion of the reference flight path. 

(2) Q represents the airplane position on 

the measured flight path at which the noise 
was emitted and observed as PNLTM at the 

noise measuring station K. Q

r

is the cor-

responding position on the reference flight 
path, and K

r

the reference measuring station. 

QK and Q

r

K

r

are, respectively, the measured 

and reference noise propagation paths. In 
this case K

r

is only specified as being on a 

particular Lateral line; K

r

and Q

r

are there-

fore determined from the assumptions that 
QK and Q

r

K

r

: 

(i) Form the same angle 

q 

with their re-

spective flight paths; and 

(ii) Form the same angle 

y 

with the 

ground. 

N

OTE

: For the lateral noise measurement, 

sound propagation is affected not only by in-
verse square and atmospheric attenuation, 
but also by ground absorption and reflection 
effects which depend mainly on the angle 

y

. 

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