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796 

14 CFR Ch. I (1–1–18 Edition) 

Pt. 36, App. A 

A36.9.3.2.1 The one-third octave band levels 

SPL(i) comprising PNL (the PNL at the mo-
ment of PNLTM observed at K) must be ad-
justed to reference levels SPL(i)

r

as follows: 

A36.9.3.2.1(a) For calculations using the 

English System of Units: 

SPL(i)

r

= SPL(i) + 0.001[a(i)¥a(i)

0

]QK 

+ 0.001a(i)

0

(QK¥Q

r

K

r

+ 20log(QK/Q

r

K

r

In this expression, 
(1) The term 0.001[a(i)¥a(i)

0

]QK is the ad-

justment for the effect of the change in 
sound attenuation coefficient, and a(i) and 

a

(i)

0

are the coefficients for the test and ref-

erence atmospheric conditions respectively, 

determined under section A36.7 of this appen-
dix; 

(2) The term 0.001a(i)

0

(QK ¥ Q

r

K

r

) is the ad-

justment for the effect of the change in the 
noise path length on the sound attenuation; 

(3) The term 20 log(QK/Q

r

K

r

) is the adjust-

ment for the effect of the change in the noise 
path length due to the ‘‘inverse square’’ law; 

(4) QK and Q

r

K

r

are measured in feet and 

a

(i) and a(i)

0

are expressed in dB/1000 ft. 

A36.9.3.2.1(b) For calculations using the 

International System of Units: 

SPL(i)

r

= SPL(i) + 0.01[a(i)¥a(i)

0

]QK 

+ 0.01a(i)

0

(QK ¥ Q

r

K

r

+ 20 log(QK/Q

r

K

r

In this expression, 

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