788 

14 CFR Ch. I (1–1–19 Edition) 

Pt. 36, App. A 

SPL

′

(i,k), may be determined from the nar-

row band analysis and used to compute a re-
vised tone correction factor for that par-
ticular one-third octave band. Other methods 
of rejecting spurious tone corrections may be 
approved. 

A36.4.3.2 The tone correction procedure 

will underestimate EPNL if an important 
tone is of a frequency such that it is re-
corded in two adjacent one-third octave 
bands. An applicant must demonstrate that 
either: 

(a) No important tones are recorded in two 

adjacent one-third octave bands; or 

(b) That if an important tone has occurred, 

the tone correction has been adjusted to the 
value it would have had if the tone had been 

recorded fully in a single one-third octave 
band. 

A36.4.4 Maximum tone-corrected perceived 

noise level 

A36.4.4.1 The maximum tone-corrected per-

ceived noise level, PNLTM, must be the max-
imum calculated value of the tone-corrected 
perceived noise level PNLT(k). It must be 
calculated using the procedure of section 
A36.4.3. To obtain a satisfactory noise time 
history, measurements must be made at 0.5 
second time intervals. 

N

OTE

1: Figure A36–2 is an example of a fly-

over noise time history where the maximum 
value is clearly indicated. 

N

OTE

2: In the absence of a tone correction 

factor, PNLTM would equal PNLM. 

A36.4.4.2 After the value of PNLTM is ob-

tained, the frequency band for the largest 
tone correction factor is identified for the 
two preceding and two succeeding 500 ms 
data samples. This is performed in order to 
identity the possibility of tone suppression 
at PNLTM by one-third octave band sharing 
of that tone. If the value of the tone correc-
tion factor C(k) for PNLTM is less than the 

average value of C(k) for the five consecutive 
time intervals, the average value of C(k) 
must be used to compute a new value for 
PNLTM. 

A36.4.5 

Duration correction. 

A36.4.5.1 The duration correction factor D 

determined by the integration technique is 
defined by the expression: 

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