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the noise levels obtained at the flyover measurement point.
5.4.2 The measured flight path shall be corrected by an
amount equal to the difference between the applicant's
predicted flight paths for the test conditions and for the noise
certification reference conditions.
Note.- Necessary corrections relating to aeroplane flight
path or performance may be derivedfiom approved data other
than certification test data.
5.4.2.1 The flight path correction procedure for approach
noise shall be made with reference to a fixed aeroplane reference
height and the reference approach angle. The effective
perceived noise level correction shall be less than 2 EPNdB to
allow for:
a) the aeroplane not passing vertically above the measuring
point;
b) the difference between the reference height and the
height of the aeroplane's ILS antenna from the approach
measuring point; and
c) the difference between the reference and the test
approach angles.
Note.- Detailed correction requirements are given in
Section 9 of this appendix.
5.4.3 Test results on specific measurement shall not be
accepted if the difference in EPNL computed from measured
data and that corrected to reference conditions exceeds
15 EPNdB.
5.4.4 If aeroplane sound pressure levels do not exceed the
ambient sound pressure levels by at least 10 dB in any
one-third octave band approved corrections for the contribution
of ambient sound pressure level to the observed sound
pressure level shall be applied.
5.5 Validity of results
5.5.1 Three average EPNL values and their 90 per cent
confidence limits shall be produced from the test results, each
such value being the arithmetical average of the corrected
acoustical measurements for all valid test runs at the appropriate
measurement point (take-off, approach or sideline). If more
than one acoustic measurement system is used at any single
measurement location (such as for the symmetrical sideline
measuring points), the resulting data for each test run shall be
averaged as a single measurement.
5.5.2 The minimum sample size acceptable for each of
the three certification measuring points shall be six. The samples
shall be large enough to establish statistically for each of
the three average noise certification levels a 90 per cent confidence
limit not exceeding k1.5 EPNdB. No test result shall
be omitted from the average process unless otherwise specified
by the certification authorities.
5.5.3 The average EPNL values and their 90 per cent confidence
limits obtained by the foregoing process shall be those
by which the noise performance of the aeroplane is assessed
against the noise certification criteria, and shall be reported.
APP 1-13
Annex 16 - Environmental Protection
6. NOMENCLATURE
6.1 Symbols and units
Volume 1
Symbol
antilog
C(k)
D
EPNL
Note.- The meanings of the various symbols in this
appendix are as follows. It is recognized that dzflerences may
exist in the units and meanings of similar symbols in
Appendix 2.
Unit Meaning
- Antilogarithm to the base 10.
dB Tone correction factor The factor to be added to PNL(k) to account for the presence of spectral irregularities
such as tones at the k-th increment of time.
s Duration time. The length of the significant noise time history being the time interval between the limits of 41)
and 42) to the nearest second.
dB Duration correction. The factor to be added to PNLTM to account for the duration of the noise.
EPNdB Effective perceived noise level. The value of PNL adjusted for both the spectral irregularities and the duration
of the noise. (The unit EPNdB is used instead of the unit dB.)
Hz Frequency. The geometrical mean frequency for the i-th one-third octave band.
dB Delta-dB. The difference between the original sound pressure level and the final background sound pressure
level in the i-th one-third octave band at the k-th interval of time.
dB dB-down. The level to be subtracted from PNLTM that defines the duration of the noise.
% Relative humidify The ambient atmospheric relative humidity.
- Frequency band index. The numerical indicator that denotes any one of the 24 one-third octave bands with
geometrical mean frequencies from 50 to 10 000 Hz.
Time increment index. The numerical indicator that denotes the number of equal time increments that have
elapsed from a reference zero.
- Logarithm to the base 10.
- Noy discontinuify coordinate. The log n value of the intersection point of the straight lines representing the
variation of SPL with log n.
M(b), M(c), etc. -
n nOY
n(j,k) n0Y
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