787 

Federal Aviation Administration, DOT 

Pt. 36, App. A 

(j) Step 10: Designate the largest of the 

tone correction factors, determined in Step 
9, as C(k). (An example of the tone correction 
procedure is given in the current advisory 
circular for this part). Tone-corrected per-
ceived noise levels PNLT(k) must be deter-
mined by adding the C(k) values to cor-
responding PNL(k) values, that is: 

PNLT(

k

) = PNL(

k

) + 

C

(

k

) 

For any i-th one-third octave band, at any k- 
th increment of time, for which the tone cor-

rection factor is suspected to result from 
something other than (or in addition to) an 
actual tone (or any spectral irregularity 
other than airplane noise), an additional 
analysis may be made using a filter with a 
bandwidth narrower than one-third of an oc-
tave. If the narrow band analysis corrobo-
rates these suspicions, then a revised value 
for the background sound pressure level 

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