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with measurement and analysis system accuracy as phone during all measurements of aeroplane noise when the
statcd in 3.3; wind speed is in excess of 1 I km/h (6 kt). Corrections for any
insertion loss vroduced by the wind screen, as a function of
b) tripods or similar microphone mountings that n~inimize frequency. shall be applied to the measured data and the
interference with the sound being measured; corrections applied shall be reported.
c) recording and reproducing equipment characteristics,
frequency response, and dynamic range compatible with 3.4 Analysis equipment
the response and accuracy requirements of 3.3;
3.4.1 A frea.u encv. analvsis of the acoustical si-m al shall
d) acoustic calibraton using sine wave or broadband noise be performed in a manner equivalent to using one-third octave
of known sound pressure level. If broadband noise is filters complying with the recommendations given in IEC
used, the signal shall be described in terms of its average Publication No. 225.3
and maxi&&n root-mean-square (rms) value for no;-
overload signal level; Note.- The text and specifications of IEC Publication
No. 22j3 entitIed "Octave, Half-Octave and Third-Octave Band
e) analysis equipment with the response and accuracy Filters Intendedfor the Analysis of Sounds and Wbrations " are
requirements of 3.4. incorporated by reference into this appendix and are made a
part hereof5
3.3 Sensing, recording and
reproducing equipment 3. As amended.
4. This publication was first issued in 1965 by the Central Office of the
3.3.1 The sound produced by the aeroplane shall be International Electrotechnical Commission, 3 rue de Varembe, Geneva,
recorded in such a way that the complete information, time Switzerland.
5. This publication was first issued in 1966 by the Central Office of the history included, is retained. A magnetic tape recorder is International Electrotechnical Commission, 3 rue de VarembC, Geneva,
acceptable. Switzerland.
APP 1-3 2411 1/05
Annex 16 - Environmental Protection Volume I
3.4.2 A set of 24 consecutive one-third octave filters
or its equivalent shall be used. The first filter of the set shall
be centred at a geometric mean frequency of 50 Hz and the last
shall be centred at a geometric mean frequency of 10 kHz.
3.4.3 The analyser indicating device shall be analogue,
digital, or a combination of both. The preferred sequence of
signal processing shall be:
a) squaring the one-third octave filter outputs;
45 dB in terms of the difference between full-scale output
level and the maximum noise level of the analyser equipment.
3.4.9 The complete electronic system shall be subjected
to a frequency and amplitude electrical calibration by the use
of sinusoidal or broadband signals at frequencies covering the
range of 45 to 11 200 Hz, and of known amplitudes covering
the range of signal levels furnished by the microphone. If
broadband signals are used, they shall be described in terms of
their average and maximum rms values for a non-overload
signal level.
b) averaging or integrating; and
c) linear to logarithmic conversion. 3.5 Noise measurement procedures
The indicating device shall have a minimum crest factor
capacity of 3 and shall measure, within a tolerance of *1.0 dB,
the true root-mean-square (rms) level of the signal in each of
the 24 one-third octave bands. If other than a true rms device
is utilized, it shall be calibrated for nonsinusoidal signals and
time varying levels. The calibration shall provide means for
converting the output levels to true rms values.
3.4.4 The dynamic response of the analyser to input signals
of both full-scale and 20 dB less than full-scale amplitude
shall conform to the following two requirements:
a) the maximum output value shall read 4 dB * 1 dB less
than the value obtained for a steady state signal of the
same frequency and amplitude when a sinusoidal pulse
of 0.5 s duration at the centre frequency of each
one-third octave band is applied to the input;
b) the maximum output value shall exceed thc final steady
state value by 0.5 * 0.5 dB when a steady state sinusoidal
signal at the geometrical mean frequency of each
one-third octave band is suddenly applied to the analyser
input and held constant.
3.4.5 A single value of the rms level shall be provided
every 0.5 0.01 s for each of the 24 one-third octave bands.
The levels from all of the 24 one-third octave bands shall be
obtained within a 50 ms period. No more than 5 ms of data
from any 0.5 s period shall be excluded from the measurement.
3.4.6 The amplitude resolution of the analyser shall be
0.50 dB or less.
3.4.7 Each output level from the analyser shall be accurate
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