Figure 1. Measurement and reporting of background

Figure 1. Measurement and reporting of background
Measure background noise for 10 seconds using both
left and right microphones. (2.3.1)
Re-measure
background noise
(2.3.1)
Any transient
disturbance? (2.3.1)
NO
Report maximum A-weighted
SPL from both Left and Right
microphones.
L_bgn=MAX(Max_SPL_left),
(Max_SPL_right)) (2.3.1)
YES
Report 1/3 octave
frequency spectrum at
time corresponding to
L_bgn (2.3.1)
Report maximum to
minimum range of the
background noise at
each microphone.
L_bgn, p-p (2.3.1)
Figure 1. Measurement and reporting of background noise.
Conduct measurement
according to 3.3
Is L_bgn, p-p less or equal to 2 dB? (2.3.1)
NO
Is L according to Table 1
greater or equal to 10 dB? (2.3.2)
NO
STOP. No valid
measurement
YES
Carry out SPL correction
according to Table 1 for each
individual measurement j . (2.3.2)
YES
Report L_testcorr, j for each
individual test run j. (2.3.2)
Figure 2. Vehicle A-Weighted sound pressure level measurement correction criteria.
Conduct measurement
according to 3.3
Is background level in each one-third octave
band of interest at least 6 dB greater than the
corresponding one-third-octave band
measured according to 2.3.1 ? (2.3.3)
NO
STOP. No valid
measurement of
one-third octave
band results
YES
Is overall sound pressure level measured according
to 3.3 at least 10 dB greater than the corresponding
overall sound pressure level of the background
noise measured according to 2.3.1 ? (2.3.3)
NO
STOP. No valid
measurement of
one-third octave
band results
YES
Report one-third-octave band
results for each band of interest
for each individual test run j.
(3.4)
Figure 3. Background noise requirements for analysis in one-third-octave bands
Select Method of Testing
(4.1)
Method A
Method B
Method C
Method D
Method E
Method F
Select instrumentation and analyzer settings
appropriate to the selected method and nature
of the signal measured (4.2)
NO
Was Method B,
C, D, or E
selected?
Was Method
A selected?
YES
YES
See Figure 4b
See Figure 4c
NO
See Figure 4d
Figure 4a. Test procedures for measurement of frequency shift
Carry out four measurements at each
speed specified in 4.3.1. Record two
seconds of time data centered on the
maximum sound pressure level for
each measurement. (4.4.1)
Use data from the Left or Right microphone for
further analysis corresponding to the microphone
with the lowest average sound pressure level .
Use a Hanning window and at least a 66.6% overlap
to calculate an autopower spectrum according to
the analyzer settings of 4.2
Calculate the final spectra by energetically
averaging the four individual spectra. Calculate the
vehicle speed by mathematically averaging the
measured vehicle speeds
Report vehicle speed and frequency information at
each vehicle speed of test
Calculate frequency shift according to equation 1 in
4.5 and report frequency shift according to Table 4
of 4.5
Figure 4b. Test procedures for measurement of frequency shift, Method A
Carry out one measurement at each
speed specified in 4.3.2, 4,3,3, or 4.3.4
as appropriate for the method selected.
Record five seconds of time data for
each measurement. (4.4.2)
Use data from the Left or Right microphone for
further analysis corresponding to the
microphone with the lowest sound pressure
level.
Use a Hanning window and at least a 66.6% overlap
to calculate an autopower spectrum according to
the analyzer settings of 4.2
Report vehicle speed and frequency information at
each vehicle speed of test
Calculate frequency shift according to equation 1 in
4.5 and report frequency shift according to Table 4
of 4.5
Figure 4c. Test procedures for measurement of frequency shift, Methods B, C, D, and E
Carry out measurements as
mutually agreed between the
Technical Service and the
Manufacturer (4.3.5)
Report vehicle speed and frequency information at
each vehicle speed of test
Calculate frequency shift according to equation 1 in
4.5 and report frequency shift according to Table 4
of 4.5
Figure 4d. Test procedures for measurement of frequency shift, Method F
Range
dB
Time
Figure 5. Determination of the range of background noise
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