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path (Figure AT-I2 a)), and XrYr that of the cornsponding
rejkrence flight path (Figure A2-11 b)).
b) Q represents the aeroplane position on the measured
flight path at which the noise was emitted and observed
as PNLTM UI [he noise measuring slulion K. Q, is the
corresponding position on the reference flight path and
K, the rtference measuring station. QK and Q& are
respectively the measured and reference noise propagation
paths. In this case K, is only specijed as being
on a particular lateral line; K, and Q, are therejbre
foundfrom the assumptions that QK and Q$,:
I) form the same angle 0 with their respective flight
paths, and
2) form the same angle yr with the ground
Note 3.- In the particular case of lateral noise measurement,
sound propagation is affected not only by "inverse
square" and atmospheric attenuation, but also by ground
absorption and rejlection effects which depend mainly on the
angle yr.
9.3.2.1 The one-third octave band levels SPL(i) comprising
PNL (the PNL at the moment of PNLTM observed at K)
shall be adjusted to reference levels SPL(i), as follows:
2411 1/05 APP 2-26
Appendix 2 Annex 16 - Environmental Protection
Specified take-off measurement distance
f - b
Measurement made over this range
4
Figure At-8. Typical take-off profrle
P
I
0
Approach
measurement distance
4 b
Measurement made over this range
4 F
Figure A2-9. Typical approach profile
APP 2-27
Annex 16 - Environmental Protection Volume Z
Figure A2-10. Profile characteristics influencing sound level
Q
Runway centre line
----
K
a - Measured flight path
Reference
------- way centre line at specified distance
K ,
b - Reference flight path
Figure A2-11. Lateral measurement - determination of reference station
APP 2-28
Appendix 2 Annex 16 - Environmental Protection
In this expression:
- the term 0.01 [a(i) - a(i:),]Q K accounts for the effect
of the change in sound attenuation coefficient, and a(z]
and a(i), are the coefficients for the test and reference
atmospheric conditions respectively, obtained from
Section 7;
- the term 0.01 a(i), (QK - Q,.Kr) accounts for the effect
of the change in the noise path length on the sound
attenuation;
- the term 20 log (QWQ,.K,,) accounts for the effect of the
change in the noise path length due to the "inverse
square" law;
- QK and Q,.K,. are measured in metres and a(i) and a(i),
are in dB/100 m.
9.3.2.1.1 The corrected values SPL(i), shall be converted
to PNLT,, and a correction term calculated as follows:
A, = PNLT,. - PNLTM
9.3.2.1.2 A, shall be added algebraically to the EPNL
calculated from the measured data.
9.3.2.2 If, during a test flight, several peak values of
PNLT are observed which are within 2 dB of PNLTM, the
procedure defmed in 9.3.2.1 shall be applied at each peak and
the adjustment term calculated as in 9.3.2.1 shall be added to
each peak to give corresponding adjusted peak values of
PNLT. If these peak values exceed that at the moment of
PNLTM, the maximum value of such exceedance shall be
added as a further adjustment to the EPNL calculated from the
measured data.
9.3.3 Adjustments to duration correction
9.3.3.1 Whenever the measured flight paths andor the
ground velocities in the test conditions differ from the reference
flight paths andlor the ground velocities in the reference
conditions, duration adjustments shall be applied to the EPNL
values calculated from the measured data. The adjustments
shall be calculated as described below.
9.3.3.2 Referring to the flight path shown in Figure A2-10,
the adjustment term shall be calculated as follows:
A, = -7.5 log (QWQrKr) + 10 log (VN,)
which represents the adjustment to be added algebraically to
the EPNL calculated from the measured data.
9.3.4 Source noise adjustments
9.3.4.1 The source noise adjustment shall be applied to
take account of differences between the parameters affecting
engine noise measured in the certification flight tests and those
calculated or specified in the reference conditions. The adjustment
shall be determined from manufacturers' data approved
by the certificating authority.
Note.- Typical data are illustrated in Figure A2-12 which
shows a curve of EPNL versus the engine control parameter p,
the EPNL data being corrected to all the other relevant reference
conditions (aeroplane mass, speed and altitude, air temperature)
and for the dzference in noise between the installed
engine and the flight manual standard of engine at each value
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