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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