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suppression at PNLTM by one-third octave band sharing of
that tone. If the value of the tone correction factor C&) for
PNLTM is less than the average value of C(k) for the five consecutive
time intervals, the average value of C&) shall be used
to compute a new value for PNLTM.
4.5 Duration correction
4.5.1 The duration correction factor, D, determined by the
integration technique shall be defined by the expression:
where T is a normalizing time constant, PNLTM is the maximum
value of PNLT, tl is the first point of time after which
PNLT becomes greater than PNLTM - 10 and t2 is the point
of time after which PNLT remains constantly less than
PNLTM - 10.
4.5.2 Since PNLT is calculated from measured values
of SPL, there will, in general, be no obvious equation for
PNLT as a function of time. Consequently, the equation shall
be rewritten with a summation sign instead of an integral sign
as follows:
log PNL 1 (3 ' g ~ tan tilog -
k= 0 1"
- PNLTM
where At is the length of the equal increments of time for
which PNLT(k) is calculated and d is the time interval to the
nearest 0.5 seconds during which PNLT(k) remains greater or
equal to PNLTM - 10.
4.5.3 To obtain a satisfactory history of the perceived
noise level,
a) half-second time intervals for At, or
b) a shorter time interval with approved limits and constants,
shall be used.
4.5.4 The following values for T and At shall be used in
calculating D in the procedure given in 4.5.2:
T = 10 s, and
At = 0.5 s
Using the above values, the equation for D becomes
2d
D = 10 log antilog PNLT(k) - PNLTM - 13
10 [k=O -1
where d is the duration time defined by the points corresponding
to the values PNLTM - 10.
4.5.5 If in the procedures given in 4.5.2, the limits of
PNLTM - 10 fall between the calculated PNLT(k) values (the
usual case), the PNLT(k) values defining the limits of the duration
interval shall be chosen from the PNLT(k) values closest
to PNLTM - 10. For those cases with more than one peak
value of PNLT(k), the applicable limits must be chosen to
yield the largest possible value for the duration time.
4.6 Effective perceived noise level
The total subjective effect of an aircraft noise event, designated
"effective perceived noise level", EPNL, shall be equal to the
algebraic sum of the maximum value of the tone corrected perceived
noise level, PNLTM, and the duration correction D. That
is:
EPNL = PNLTM + D
where PNLTM and D are calculated in accordance with the
procedures given in 4.2, 4.3, 4.4 and 4.5.
4.7 Mathematical formulation
of noy tables
4.7.1 The relationship between sound pressure level
(SPL) and the logarithm of perceived noisiness is illustrated in
Table A2-3 and Figure A2-3.
4.7.2 The important aspects of the mathematical
formulation are:
a) the slopes (M(b), M(c), M(4 and M(e)) of the straight
lines;
b) the intercepts (SPL(b) and SPL(c)) of the lines on the
SPL axis; and
24111105 APP 2-12
Appendix 2 Annex I6 - Environmental Protection
Flyover time t, seconds
Figure A2-2. Example of perceived noise level corrected for tones as a function of aeroplane flyover time
Figure A2-3. Perceived noisiness as a function of sound pressure level
APP 2-13
Annex 16 - Environmental Protection Volume I
Table A2-3. Constants for mathematically formulated noy values
BAND f
(i) Hz
SPL SPL
(a) (6)
91.0 64
85.9 60
87.3 56
79.0 53
79.8 5 1
76.0 48
74.0 46
74.9 44
94.6 42
SPL
(4
SPL SPL
(4 (el
49 55
44 5 1
3 9 46
34 42
30 3 9
27 36
24 3 3
2 1 3 0
18 27
APP 2-14
Appendix 2 Annex I6 - Environmental Protection
c) the coordinates of the discontinuities, SPL(a) and
log n(a); SPL(d) and log n = -1.0; and SPL(e) and
log n = log (0.3).
4.7.3 The equations are as follows:
a) SPL 1 SPL(a)
n = antilog {M(c) [SPL - SPL(c)]}
b) SPL(b) 5 SPL < SPL(a)
n = antilog {M(b) [SPI, - SPI,(h)])
C) SPL(e) 5 SPL < SPL(b)
n = 0.3 antiloglo {M(e) [SPL - SPL(e)])
d) SPL(LJ) < SPL < SPL(e)
n = 0.1 antilog (M(4 [SPL - SPL(d)]j
4.7.4 Table A2-3 lists the values of the constants necessary
to calculate perceived noisiness as a function of sound
pressure level.
5. REPORTING OF DATA TO THE
CERTIFICATING AUTHORITY
5.1 General
5.1.1 Data representing physical measurements or corrections
to measured data shall be recorded in permanent form
and appended to the record.
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