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the following cbaractenstics:
a) dynamic range of 50 dB minimum in the octave or onethird
octave bands;
b) tape speed accuracy within M.2 per cent of rated speed;
C) WOW and flutter (peak to peak) less than 0.5 per cent of
tape speed;
d) maximum third harmonic dislortioo less than 2 per cent.
4.3 2.3.1 Microphone
Frequency response calibration should be performed prior to
the test senes and a subsequent post-calibration sbolrld be
performed wtthin one monlh of the precalibration. wlth
additional calibrations made when shock or damage is suspected.
Response calibration should cover the range of at least
45 Hz to 11 200 Hz. Pressure respmse characteristics of the
microphone should be corrected to obtain random incidence
calibration.
a) A cnlibration tapc. a recording of broadband noise or a
sweep of sinuso~dal signals over a minimum frequency
range of 45 Hz to 11 200 Hz should be rccordcd in the
Acld or in thc laboratory at the beginning and end of
cach test. The tape should also includc signals at thc
frequencies cmployed dur~ngs ound pressure sensitivity
checks as defined below.
24/11/05 ATT C-2
Attachmew C Annex 16 - Emimnmental Protertion
Calibration instrumentation
I
Source of
known sound ---
pressme level
and frequency
1 Frequency-r~lpc~hee ck
Signal generator
1
IData
acquisition and data-reduction insbvmentalion
Data acquisition I
I Data reducbon
I
I
I
I ---- I
I I
I I
I I
preamplifier midi tioning re&r anal yser
1 I
Flgure C-I. Nolse measurement system
ATT C-3
c n
u A
V
0
-20 m- - -*I
0
'3 n n
V
f
! i
f x
0 2 0 m
I
I
3 -V
Figure C-2. Rectangle of noise survey measurement positions
Annex 16 - Environmental Protection Volunlp 1
b) This calibr~tion signal. an insert voltage, should be
applicd to the input and should i~rcludca ll aig~ralc onditioning
prcampl~fiers. networks and recorder elcctronics
used to record acoustlc data. In nddition. n
"shorlcd input" (i.e. microphone pressure sensitive
element replaced with equivalent electrical impedance)
recording of at least 20 s should be made as a check on
system dynam~c range and nolsc floor.
C) Sound prcssure sensstivity cabibra~ronsw ith the arrangements
shown in Figure C-1 should bc made in the field
for each micmphone prior to begimrng and after cornpletion
of measurements each day. Thcse calibrations
should bc made using a cal~bratorp roducing a known
and constant-amplitude sound pressure level at onc or
more one-third octave band centre frequencies, spccjfied
in reference 1 1 in the frequcncy rangc from 45 Hz to
11 200 Hz. A barometric correction should bc applicd as
requircd. Calibrators employed should be precise at least
to within *O.S dB and should hnve a calibration obta~ned
according to rcferenecs 6 to 9 (see 4-61.
d) Each reel of tape should have comparable responsc and
background noise to the calibration tape. A constant
amplrtude sine wave should be recordd at the start of
each reel of tape. for reel-to-reel sound prcssure sensitivity
comparisons. Tbc kquency of this sine wave
should bc wiihio the same frequency range as used for
sound prcssure sensitivity checks. A separate voltage
insert dcvice or an acoustic callbralor may be. used for
this purpose. 1f an acousttc calibrator is used. it should
he cmfully -seated" and corrections for ambient
pressurc should be madc so that effects of pressure on
calibrator nnd microphone response are eliminated.
e) Battery-driven tape recorders should be checked at
frequent intervals dunng a test to ensure good battery
condition. Tape recorders should not be moved whrlc
recordirlg IS In progress unless it has been established
that such movements will no! change tape recordcr
charac~enstrcs.
Dsta reduction equipnicnt should be calibrated with electrical
srgnals of known arnpli!udc either at a senes of discretc
frequencies or with broadbnnd signals coverlng the frcqucncy
range of 45 Hz to l l 200 Hz
4.3.2.4 Data ~z.clr~c/ion
4.3.2.4.1 The data reduction system of Figure C-1
should provide one-third or one octave hand sound prcssure
lcvcls. Analyser filters should comply with requirements of rcfcrence
12 (Class I I for octave band filtcrs and Class 111 for
ow-third octave band filters). Analyscr amplihdc rcsoh~rion
should be no worse than 0.5 dB: dynamic range should be a
m~nimumo f 50 dB betwccn full scale and the root-mean-square
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