AFRIMETS.AUV.A-S1 Final Report - BIPM · AFRIMETS.AUV.A-S1 Final Report 10 December 2015 ... Danuta...
Transcript of AFRIMETS.AUV.A-S1 Final Report - BIPM · AFRIMETS.AUV.A-S1 Final Report 10 December 2015 ... Danuta...
NMISA-14-00270
AFRIMETS.AUV.A-S1
Final Report
10 December 2015
Author: Riaan Nel (NMISA, pilot)
Co-authors: Salvador Barrera-Figueroa (DFM) Danuta Dobrowolska (GUM) Zemar M. Defilippo Soares (INMETRO) Anderson K. Maina (KEBS) Christian Hof (METAS)
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ABSTRACT
This is the Final report of the AFRIMETS.AUV-S1 comparison of the pressure sensitivity, modulus and
phase, of LS2aP microphones in the frequency range 1 Hz to 31,5 kHz in accordance with IEC 61094-2.
Six National Metrology Institutes from three different Regional Metrology Organisations participated in
the comparison for which two LS2aP microphones were circulated simultaneously to all the participants
in a hybrid-star configuration. The comparison reference values were calculated as the weighted mean
for modulus and phase for each individual microphone.
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CONTENTS
ABSTRACT .............................................................................................................................................. 2
1. INTRODUCTION ............................................................................................................................ 5
2. TECHNICAL PROTOCOL ..................................................................................................................... 5
3. PARTICIPANTS ................................................................................................................................... 6
4. METHODS .......................................................................................................................................... 6
5. STABILITY OF MICROPHONES ........................................................................................................... 6
6. RESULTS REPORTED ........................................................................................................................ 13
7. ANALYSIS OF RESULTS & OUTLIERS ................................................................................................ 14
8. COMPARISON REFERENCE VALUES ................................................................................................. 20
9. DEGREES OF EQUIVALENCE ............................................................................................................ 24
10. CONCLUSIONS ............................................................................................................................. 36
11. RECOMMENDATIONS ................................................................................................................. 36
12. ACKNOWLEDGEMENTS ............................................................................................................... 36
13. REFERENCES ................................................................................................................................ 37
ANNEX A PARTICIPANT CAPABILITIES .................................................................................................. 38
ANNEX B PARTICIPANT METHODS ....................................................................................................... 39
B.1 DFM ......................................................................................................................................... 39
B.2 GUM ........................................................................................................................................ 40
B.3 INMETRO ................................................................................................................................. 41
B.4 KEBS ........................................................................................................................................ 45
B.5 METAS ..................................................................................................................................... 47
B.6 NMISA ..................................................................................................................................... 48
ANNEX C PARTICIPANT REPORTED RESULTS ........................................................................................ 49
C.1 DFM ......................................................................................................................................... 49
C.2 GUM ........................................................................................................................................ 50
C.3 INMETRO ................................................................................................................................. 52
C.4 KEBS ........................................................................................................................................ 55
C.5 METAS ..................................................................................................................................... 56
C.6 NMISA ..................................................................................................................................... 57
ANNEX D PARTICIPANT UNCERTAINTIES ............................................................................................. 58
D.1 DFM ............................................................................................................................................. 58
D.2 GUM ............................................................................................................................................. 62
D.3 INMETRO ..................................................................................................................................... 64
D.4 KEBS ............................................................................................................................................. 66
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D.5 METAS .......................................................................................................................................... 67
D.6 NMISA .......................................................................................................................................... 69
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1. INTRODUCTION
The first CIPM CCAUV key comparison, where the artefacts were LS2aP microphones, was the
CCAUV.A-K3 [1] , as agreed to in October 2001. The key comparison started early in 2003 and the final
report was published in May 2006. Subsequent Regional Metrology Organization (RMO) key
comparisons followed.
This comparison was performed under the auspices of the AFRIMETS Acoustics, Ultrasound and
Vibration Technical Committee in addressing the RMOs need for establishing measurement equivalence
in support of Calibration Measurement Capabilities (CMC) for sound pressure in air using LS2aP1
microphones.
The scope of the CCAUV.A-K3 comparison did not include the phase sensitivity of the LS2aP
microphones, whereas this comparison did. This comparisons scope also covered wider frequency
ranges than the frequency ranges specified in CCAUV.A-K3.
Six National Metrology Institutes (NMIs) from 3 different Regional Metrology Organizations (RMOs)
participated in this comparison.
This report contains information relating to all the participants measurement methods, measurement
results, the calculated Comparison Reference Values (CRVs) and the calculated Degrees of Equivalence
(DoE) for each NMI.
2. TECHNICAL PROTOCOL
This comparison was concerned only with primary methods of calibration according to IEC 61094-2:
2009 [2] for LS2aP microphones for the parameters and frequency ranges as indicated in Table 1 at
reference environmental conditions. The phase parameter was not mandatory, only modulus in the
frequency range 20 Hz to 25 kHz was mandatory.
The technical protocol [3] of this comparison was approved by the CCAUV Key Comparison Working
Group and was subsequently published on the BIPM Key Comparison Database in accordance with CIPM
MRA-D-05 [4].
Frequency spacing Frequency range Parameter
Modulus Phase 1/3 octave 1 Hz to 20 Hz 1/3 octave
20 Hz to 1 kHz CRV CRV 1/3 octave 1 kHz to 25 kHz CRV CRV 1/3 octave
25 kHz to 31,5 kHz
Optional
Table 1. Comparison scope.
1 As defined by IEC 61094-1.
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Circulation of the comparison artefacts and the comparison measurements were performed from July
2013 to October 2014.
3. PARTICIPANTS
The following NMIs participated in this comparison:
DFM, Denmark, * **
GUM, Poland *
INMETRO, Brazil *
KEBS, Kenya
METAS, Switzerland **
NMISA, South Africa (pilot)
NOTE: Participants who participated in CCAUV.A-K3 are indicated with an asterisk and participants who participated in
EUROMET.AUV.A-K3 are indicated with a double asterisk.
4. METHODS
Although the IEC 61094-2 2009 edition was specified as the basis according to which the results were to
be obtained, variations are to be expected due to varying factors (which can be due to differences in the
instrumentation and software implemented) and different approaches to the implementation of the
document standard. Explanations of each participants system, method and uncertainty matrixes are
reported in Annex B and Annex D respectively.
5. STABILITY OF MICROPHONES
The circulation pattern chosen for this comparison was a hybrid-star configuration in which the pilot
NMI performed its measurements first. The microphones where then circulated to two subsequent
participating NMIs, after which it was returned to the pilot NMI for stability measurements. This
circulation pattern was followed until all the participants had the opportunity to perform their
measurements.
Two LS2aP microphones where chosen in order to establish redundancy, in the event that one
microphone got damaged. Having two circulating microphones also served as some measure of checking
consistency of the reported results.
At the very last stage of the comparison, after all the participants performed their measurements, one
of the microphones s/n: 2787487, was received back by the pilot NMI with a finger print on the
diaphragm. Subsequent investigations revealed that the event/incident must have occurred sometime
during the return shipping process of the microphones after the last participant have performed their
measurements. This event had no influence on the last participants results.
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The two microphones were periodically measured by the pilot NMI for stability. Figures 1 and 3 illustrate
the deviation from the mean of all the stability measurements per microphone, for modulus and phase
respectively with the pilot NMIs uncertainty bands. Figures 2 and 4 also illustrate the deviation from the
mean per microphone for modulus and phase respectively, but without the uncertainty bands.
Figure 1. Stability of microphone 4180 s/n: 2049570, indicated as deviation from the mean of all the stability measurements, for modulus and phase, plotted with pilot NMIs uncertainties.
Figure 2. Stability of microphone 4180 s/n: 2049570, indicated as deviation from the mean of all the stability measurements, for modulus and phase, without pilot NMIs uncertainties.
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Figure 3. Stability of microphone 4180 s/n: 2787487, indicated as deviation from the mean of all the stability measurements, for modulus and phase, plotted with the pilot NMIs uncertainties.
Figure 4. Stability of microphone 4180 s/n: 2787487, indicated as deviation from the mean of all the stability measurements, for modulus and phase, without pilot NMIs uncertainties.
Figures 5 and 6 illustrate the stability and participant results of microphone 4180 s/n: 2049570, modulus
and phase respectively, over time. The stability is reported as the deviation from the first measurement
and the participants results are reported as deviation from the weighted mean (WM).
Figure 7 illustrates the stability of microphone 4180 s/n: 2049570, modulus and phase over time relative
to the first measurements.
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Figure 5. Microphone, 4180 s/n: 2049570, modulus stability over time and participant data relative to the WM.
Figure 6. Microphone, 4180 s/n: 2049570, phase stability over time and participant data relative to the WM.
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Figure 7. Microphone, 4180 s/n: 2049570, modulus and phase stability over time.
Figure 8 and 9 illustrates the stability and the participant results of microphone 4180 s/n: 2787487,
modulus and phase respectively, over time. The stability is reported as the deviation from the first
measurement while the participants results are reported as deviation from the WM.
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Figure 8. Microphone, 4180 s/n: 2787487, modulus stability over time and participant data relative to
the WM.
Figure 9. Microphone, 4180 s/n: 2787487, phase stability over time and participant data relative to the WM.
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Figure 10 illustrates the stability of microphone 4180 s/n: 2787487 as modulus and phase over time
relative to the first measurements.
Figure 10. Microphone, 4180 s/n: 2787487, modulus and phase stability over time.
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6. RESULTS REPORTED
All NMIs reported their results utilising their standard certificate formats and by completing and
submitting a provided reporting template. Only the results as reported in the completed reporting
templates were used for calculation and reporting purposes of this comparison. It was the responsibility
of the participating NMI to ensure that the data transfer was correct.
In addition to the modulus and phase results, all participants were required to report the lump
parameters of the two microphones. Tables 2 and 3 indicate the reported values per microphone for
each NMI.
Table 2. Lump parameters reported by the participants for microphone 4180 s/n: 2049570. (n.a. * indicates measurements were performed at reference conditions)
Table 3. Lump parameters reported by the participants for microphone 4180 s/n: 2787487. (n.a. * indicates measurements were performed at reference conditions)
Annex C reports on all the participants results and their associated uncertainties as received by the pilot
NMI.
Lump paramters NMISA DFM GUM KEBS METAS INMETRO Unit
Front volume 32,0812 32,4 33,1 33,4 32,38 32,29 mm3
Front cavity depth 0,477 0,483 0,477 0,5 0,48 0,473 mm
Equivalent volume 9,7 8,9 8,3 7,1 9,2 9,98 mm3
Resonant frequency 21,094 20,9 20,809 22,5 19,2407 22,000 kHz
Loss factor 1,04 1,1 1,16 1,07 1,068 1,07
Static pressure coefficient @ 250 Hz -0,00615 -0,00545 -0,0052 -0,007 n,a,* -0,0052 dB/kPa
Temperature coefficient @ 250 Hz -0,00116 0,00093 -0,0012 -0,002 n,a,* -0,0011 dB/K
2049570
Lump paramters NMISA DFM GUM KEBS METAS INMETRO Unit
Front volume 32,1019 31,05 31,6 33,2 31,99 31,47 mm3
Front cavity depth 0,47 0,477 0,471 0,5 0,471 0,464 mm
Equivalent volume 7,9 8,2 8,3 6,9 9,2 9,23 mm3
Resonant frequency 23,491 23,3 23,107 22,5 21,2143 22,000 kHz
Loss factor 1,05 1,00 1,29 1,07 1,108 1,07
Static pressure coefficient @ 250 Hz -0,00544 -0,0052 -0,0052 -0,007 n,a,* -0,0052 dB/kPa
Temperature coefficient @ 250 Hz -0,00116 -0,0012 -0,0012 -0,002 n,a,* -0,0011 dB/K
2787487
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7. ANALYSIS OF RESULTS & OUTLIERS
All the submitted results of the participants were evaluated by using the chi-squared (2) method [4] for
consistency and to identify outliers. In brief, the WM was calculated using Equation 1, and the
associated Weighted Uncertainty (WU) was calculated as per Equation 2. Thereafter a consistency test
was performed with a probability of 5 % that a result will be discrepant. Should the results pass the test,
the DoE was calculated as the deviation from the WM. Discrepant results were not included in the final
calculation of the WM or the WU and the subsequent DoEs.
Equation 1. Weighted mean formula.
where
x weighted mean
ix participant result
iu participant uncertainty (k = 1) for the particular result
n number of participants
Equation 2. Weighted uncertainty formula.
where
xui weighted uncertainty associated with the particular weighted mean iu participant uncertainty (k = 1) for the particular result
n number of participants
Outliers were only identified in the submitted results of two NMIs, namely INMETRO and METAS.
Tables 4 and 5, indicates the communicated outliers.
n
ii
n
ii
i
u
u
x
x
1 2
1 2
1
2
1
1
1
n
ii
i
u
xu
15
Table 4. Identified outliers for INMETRO.
Table 5. Identified outliers for METAS.
Both NMIs, INMETRO and METAS, reviewed their results and concluded that no revised results were to
be submitted. Subsequently these data points were omitted from the calculation of the CRVs.
Figures 11 to 18 illustrate all the results relative to the WM for microphone 4180 s/n: 2049570 and
microphone 4180 s/n: 2787487 respectively. For each parameter of each microphone, the results are
first illustrated inclusive of the outlier data (modulus and phase) and then illustrated without the outlier
data (modulus and phase). Calculation of the weighted mean excluded the outliers.
Microphone Frequency range Modulus Phase
1 Hz to < 20 Hz
20 Hz to 25 kHz
> 25 kHz to 31,5 kHz 31,5 kHz 31,5 kHz
1 Hz to < 20 Hz
20 Hz to 25 kHz
> 25 kHz to 31,5 kHz 31,5 kHz 31,5 kHz
2049570
2787487
Microphone Frequency range Modulus Phase
1 Hz to < 20 Hz
20 Hz to 25 kHz
> 25 kHz to 31,5 kHz
1 Hz to < 20 Hz
20 Hz to 25 kHz 25 kHz
> 25 kHz to 31,5 kHz 31,5 kHz
2049570
2787487
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Figure 11. Modulus results for microphone 4180 s/n: 2049570 relative to the weighted mean. Calculation of the weighted mean excludes outliers. The outliers are shown in this graph.
Figure 12. Phase results for microphone 4180 s/n: 2049570 relative to the weighted mean. Calculation of the weighted mean excludes outliers. The outliers are shown in this graph.
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Figure 13. Modulus results for microphone 4180 s/n: 2049570 relative to the weighted mean. Calculation of the weighted mean excludes outliers. The outliers are not shown in this graph.
Figure 14. Phase results for microphone 4180 s/n: 2049570 relative to the weighted mean. Calculation of the weighted mean excludes outliers. The outliers are not shown in this graph.
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Figure 15. Modulus results for microphone 4180 s/n: 2787487 relative to the weighted mean. Calculation of the weighted mean excludes outliers. The outliers are shown in this graph.
Figure 16. Phase results for microphone 4180 s/n: 2787487 relative to the weighted mean. Calculation of the weighted mean excludes outliers. The outliers are shown in this graph.
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Figure 17. Modulus results for microphone 4180 s/n: 2787487 relative to the weighted mean. Calculation of the weighted mean excludes outliers. The outliers are not shown in this graph.
Figure 18. Phase results for microphone 4180 s/n: 2787487 relative to the weighted mean. Calculation of the weighted mean excludes outliers. The outliers are not shown in this graph.
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8. COMPARISON REFERENCE VALUES
The CRV is an important outcome of this comparison. The CRV was determined as the WM. Any
anomalous result identified by the pilot NMI was reported to the relevant NMI in accordance with the
CIPM MRA guidelines.
The CRVs were calculated as the WM with the associated WU. Figures 19 and 20 illustrate the modulus
and phase CRVs for microphones 4180 s/n: 2049570 and 4180 s/n: 2787487 respectively.
Figure 19. Modulus and phase CRVs of microphone 4180 s/n: 2049570.
Figure 20. Modulus and phase CRVs of microphone 4180 s/n: 2787487.
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Figures 21 and 22 illustrate the uncertainties associated with the CRVs of the modulus and phase, k = 2,
for microphones 4180 s/n: 2049570 and 4180 s/n: 2787487 respectively.
Figure 21. CRV Modulus and phase WU of microphone 4180 s/n: 2049570.
Figure 22. CRV Modulus and phase WU of microphone 4180 s/n: 2787487.
Table 6 illustrate the CRVs for microphone 4180 s/n: 2049570 for modulus and phase with the
associated uncertainties (k = 2) respectively. Table 7 illustrate the CRVs for microphone 4180 s/n:
2787487 for modulus and phase with the associated uncertainties (k = 2) respectively.
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CRVs 4180 s/n: 2049570
Frequency (Hz)
Modulus (dB re 1 V/Pa)
Uncertainty (dB)
Phase ()
Uncertainty ()
1,000 -37,202 0,159
175,97 1,68
1,259 -37,272 0,139
176,20 1,67
1,585 -37,328 0,129
176,56 1,64
1,995 -37,393 0,091
176,50 0,30
2,512 -37,445 0,081
177,00 0,29
3,162 -37,509 0,079
177,38 0,29
3,981 -37,559 0,073
177,59 0,22
5,012 -37,602 0,054
177,83 0,21
6,310 -37,639 0,049
178,08 0,21
7,943 -37,674 0,047
178,25 0,18
10,000 -37,712 0,036
178,41 0,18
12,589 -37,739 0,034
178,58 0,15
15,849 -37,760 0,029
178,72 0,13
19,953 -37,783 0,026
178,85 0,12
25,119 -37,796 0,024
178,97 0,10
31,623 -37,816 0,023
179,06 0,09
39,811 -37,828 0,021
179,13 0,09
50,119 -37,837 0,017
179,20 0,06
63,096 -37,849 0,016
179,23 0,05
79,433 -37,857 0,016
179,25 0,05
100,000 -37,865 0,016
179,24 0,05
125,893 -37,874 0,014
179,22 0,04
158,489 -37,879 0,014
179,18 0,04
199,526 -37,884 0,014
179,10 0,04
251,189 -37,891 0,014
178,99 0,04
316,228 -37,895 0,014
178,84 0,04
398,107 -37,900 0,014
178,64 0,04
501,187 -37,902 0,014
178,37 0,04
630,957 -37,904 0,014
178,03 0,04
794,328 -37,905 0,014
177,59 0,04
1 000,00 -37,905 0,014
177,03 0,04
1 258,93 -37,900 0,014
176,32 0,05
1 584,89 -37,895 0,014
175,41 0,05
1 995,26 -37,883 0,014
174,24 0,05
2 511,89 -37,860 0,014
172,76 0,05
3 162,28 -37,825 0,014
170,87 0,05
3 981,07 -37,773 0,014
168,41 0,05
5 011,87 -37,691 0,014
165,19 0,06
6 309,57 -37,570 0,015
160,90 0,08
7 943,28 -37,397 0,016
154,99 0,08
10 000,0 -37,188 0,019
146,61 0,12
12 589,3 -37,057 0,021
134,27 0,13
15 848,9 -37,379 0,025
116,43 0,17
19 952,6 -38,853 0,045
94,41 0,30
25 118,9 -41,831 0,067
74,23 0,39
31 622,8 -45,446 0,120
61,68 0,69
Table 6. Modulus and phase CRVs for microphone 4180 s/n: 2049570 with associated uncertainties.
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CRVs 4180 s/n: 2787487
Frequency (Hz)
Modulus (dB re 1 V/Pa)
Uncertainty (dB)
Phase ()
Uncertainty ()
1,000 -38,554 0,159
177,44 1,68
1,259 -38,635 0,139
177,44 1,67
1,585 -38,685 0,129
177,77 1,64
1,995 -38,743 0,091
177,61 0,30
2,512 -38,778 0,081
178,27 0,29
3,162 -38,802 0,079
178,48 0,29
3,981 -38,819 0,073
178,68 0,22
5,012 -38,827 0,054
178,87 0,21
6,310 -38,839 0,049
178,97 0,21
7,943 -38,841 0,047
179,07 0,18
10,000 -38,870 0,036
179,16 0,18
12,589 -38,881 0,034
179,28 0,15
15,849 -38,895 0,029
179,32 0,13
19,953 -38,908 0,026
179,38 0,12
25,119 -38,915 0,024
179,47 0,10
31,623 -38,923 0,023
179,50 0,09
39,811 -38,934 0,021
179,52 0,09
50,119 -38,934 0,017
179,56 0,06
63,096 -38,943 0,016
179,53 0,05
79,433 -38,947 0,016
179,52 0,05
100,000 -38,951 0,016
179,49 0,05
125,893 -38,958 0,014
179,45 0,04
158,489 -38,962 0,014
179,38 0,04
199,526 -38,965 0,014
179,30 0,04
251,189 -38,967 0,014
179,19 0,04
316,228 -38,970 0,014
179,03 0,04
398,107 -38,971 0,014
178,84 0,04
501,187 -38,972 0,014
178,57 0,04
630,957 -38,973 0,014
178,25 0,04
794,328 -38,973 0,014
177,83 0,04
1 000,00 -38,973 0,014
177,30 0,04
1 258,93 -38,968 0,014
176,63 0,05
1 584,89 -38,964 0,014
175,77 0,05
1 995,26 -38,954 0,014
174,69 0,05
2 511,89 -38,937 0,014
173,32 0,05
3 162,28 -38,909 0,014
171,56 0,05
3 981,07 -38,869 0,014
169,30 0,05
5 011,87 -38,808 0,014
166,33 0,06
6 309,57 -38,714 0,015
162,48 0,08
7 943,28 -38,583 0,016
157,22 0,08
10 000,0 -38,418 0,019
149,96 0,12
12 589,3 -38,288 0,021
139,44 0,13
15 848,9 -38,445 0,025
124,27 0,17
19 952,6 -39,414 0,045
104,31 0,30
25 118,9 -41,728 0,067
83,70 0,40
31 622,8 -44,958 0,130
68,11 0,69
Table 7. Modulus and phase CRVs for microphone 4180 s/n: 2787487 with associated uncertainties.
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9. DEGREES OF EQUIVALENCE
According to the CIPM MRA-D-05 [5] it is not a requirement to report the DoE for RMO supplementary
comparisons. The DoE have however been calculated and are reported below with the WU (red lines)
and the participants reported uncertainties (error bars). All the uncertainties indicated are for a
coverage factor of k = 2.
Figures 23 to 28 illustrate the DoE as determined for microphone 4180 s/n: 2049570. Figures 29 to 34
illustrate the DoE as determined for microphone 4180 s/n: 2787487.
Figure 23. Degrees of equivalence of DFM for modulus and phase, microphone 4180 s/n: 2049570.
25
Figure 24. Degrees of equivalence of GUM for modulus and phase, microphone 4180 s/n: 2049570.
26
Figure 25. Degrees of equivalence of INMETRO for modulus and phase, microphone 4180 s/n: 2049570.
Figure 26. Degrees of equivalence of KEBS for modulus, microphone 4180 s/n: 2049570.
28
Figure 27. Degrees of equivalence of METAS for modulus and phase, microphone 4180 s/n: 2049570.
29
Figure 28. Degrees of equivalence of NMISA for modulus and phase, microphone 4180 s/n: 2049570.
30
Figure 29. Degrees of equivalence of DFM for modulus and phase, microphone 4180 s/n: 2787487.
31
Figure 30. Degrees of equivalence of GUM for modulus and phase, microphone 4180 s/n: 2787487.
32
Figure 31. Degrees of equivalence of INMETRO for modulus and phase, microphone 4180 s/n: 2787487.
33
Figure 32. Degrees of equivalence of KEBS for modulus, microphone 4180 s/n: 2787487.
34
Figure 33. Degrees of equivalence of METAS for modulus and phase, microphone 4180 s/n: 2787487.
35
Figure 34. Degrees of equivalence of NMISA for modulus and phase, microphone 4180 s/n: 2787487.
36
10. CONCLUSIONS
Overall, the comparison progressed well and is considered successful in achieving the objectives of
establishing measurement equivalence in support of CMCs for LS2aP microphones. Thought was given
to the current trend of reporting results at exact base-10 frequencies, thereby maintaining homogeneity
and keeping with the practise in the CCAUV.A-K5 [6] comparison and IEC TC29 under which IEC 61094-2
resides.
Regarding phase sensitivity results, CCAUV.A-K3 did not require that the phase sensitivity of the
microphones to be determined and reported. This comparison was the first comparison for LS2aP
microphones to include phase sensitivity and which extend down to 1 Hz in frequency (for both modulus
and phase).
11. RECOMMENDATIONS
Some matters which may possibly aid the timeous administering of future comparisons have been
noted:
the use of couriers to transport the participants official certificates, instead of using
conventional postage systems,
making it mandatory that the measurement artefacts to be hand carried, rather than being
subjected to being handled by customs officials and courier companies (this will also eliminate
any delays caused due to arbitrary formalities).
In this comparison the modulus and phase DoEs were calculated for all results that were not identified
as being outliers. Thought must be given for treating results when either the modulus or phase is
identified as being an outlier, if the complementing non-outlying measurand should be accepted,
included and reported, seeing that modulus and phase sensitivity is a complex quantity.
12. ACKNOWLEDGEMENTS
The pilot NMIs hereby acknowledges and appreciates all the participating NMIs time and efforts in
contributing to this comparison. The author is also grateful for the assistance offered by Mr Chris
Matthee during the data analysis stages of the comparison.
37
13. REFERENCES
[1] Vicente Cutanda Henrquez and,Knud Rasmussen, "Final report on the key comparison CCAUV.A-
K3," Metrologia, vol. 43, pp. 09001, 2006.
[2] IEC 61094-2, Measurement Microphones - Part 2: Primary Method for Pressure Calibration of
Laboratory Standard Microphones by the Reciprocity Technique. International Electrotechnical
Commission, 2009.
[3] R. Nel, "Technical protocol: Open-circuit pressure sensitivity and pressure phase sensitivity according
to IEC 61094-2: 2009," CCAUV, BIPM, Tech. Rep. AFRIMETS.AUV.A-S1, 2013.
[4] M. G. Cox, "The evaluation of key comparison data," Metrologia, vol. 39, pp. 589, 2002.
[5] CIPM MRA-D-05, Measurement Comparisons in the CIPM MRA. International Committee for Weights
and Measures (CIPM), 2014.
[6] J. Avison and R. G. Barham, "Final report on key comparison CCAUV.A-K5: pressure calibration of
laboratory standard microphones in the frequency range 2 Hz to 10 kHz," Metrologia, vol. 51, pp.
09007, 2014.
38
ANNEX A PARTICIPANT CAPABILITIES
An agreement to participate questionnaire was circulated to all CCAUV -and AFRIMETS AUV members
before the comparison was registered and Table A.1 illustrates the ranges and parameters of all the
participant responses received.
Frequency NMI
Range DFM GUM KEBS METAS NMISA INMETRO
1 Hz to 20 Hz
& & & &
20 Hz to 1 kHz
& & & & &
1 kHz to 25 kHz
& & & & &
25 kHz to 31,5 kHz
& & & & Parameter keys Modulus Phase
Table A.1. Parameter summary of respondents.
39
ANNEX B PARTICIPANT METHODS
NOTE References that appear in the descriptions of a participants method description and uncertainty
matrix does not form part of the main body of text in this report.
B.1 DFM
Method
The calibration is performed as a full reciprocity calibration according to the standard IEC 61094-2
(2009) using three microphones pair-wise coupled using air filled Plane Wave couplers of four different
lengths: nominal lengths are 3 mm, 4 mm, 5 mm and 6 mm for LS2 microphones. The resulting
sensitivity is calculated using the software MP.EXE v4. Radial wave motion correction is applied.
The main component of the equipment used is a calibration apparatus type 5998 developed and built
by Brel & Kjr. The receiver microphone is connected to a preamplifier B&K 2673 with insert voltage
facilities (driven shield) and the current through the transmitter microphone is determined by the
voltage across a reference impedance in series with the microphone. This measurement impedance
(nominal 4.7 nF || 1 M) is calibrated in the frequency range 20 Hz to 40 kHz and the results
extrapolated down to 2 Hz. An external polarization voltage is supplied by a Fluke DC Voltage Calibrator
type 343A. The static pressure is measured by a barometer, Druck DPI 140 and the temperature and
humidity are measured by a Vaisala temperature and humidity probe located close to the coupler. All
measurements are conducted in a temperature controlled room at 23.0 C 1.0 C. Humidity is kept
within the range 40% - 60% RH.
The transfer function is measured using a B&K Pulse analyser in connection with SSR software (Steady
State Response). The measurements were conducted in 1/6th octave steps from 2 Hz to 31.5 kHz. Each
transfer function is determined as the average of 3 sweeps with a detector band of 0.01 dB.
The microphone front cavity depth has been measured using a laser-based measurement system. The
microphone parameters (equivalent volume, front volume, loss factor, and resonance frequency) are
determined by fitting the sensitivity obtained using the above-mentioned 4 couplers. Once determined,
the microphone parameters remain unchanged during all calibrations. Due to longitudinal modes in the
couplers the high-frequency limits for the couplers are (35, 32, 24 and 21) kHz for LS2 microphones.
Thus, at the highest frequencies above 30 kHz the results are the average of a calibration in only two
couplers.
40
B.2 GUM
Method
Open-circuit pressure sensitivity level and open-circuit pressure sensitivity phase of the microphones
was determined by the reciprocity technique described in IEC 61094-2:2009.
A single acoustic coupler of diameter 9,2928 mm and length 3,8543 mm, filled with air, without capillary
tubes, was used for the measurements.
The total volume of each microphone was measured using an acoustical technique.
GUM uses a customised version of NPLs reciprocity measurement system and software.
The acoustic impedance parameters were determined for each microphone individually. The method is
based on the optimization of the results of four sensitivity magnitude and phase determinations
obtained for four couplers of different length.
Sensitivity level and phase values at frequencies close to power line frequency and its harmonics
(47.3Hz, 50.1 Hz, 53.1 Hz, 100 Hz, 149.6 Hz, 199.5 Hz and 251 Hz), have been calculated by interpolation.
Heat conduction losses were calculated using the full Gerber (low frequency) solution, without
simplification.
No radial corrections were applied.
41
B.3 INMETRO
Method
The following equipment has been used for the calibrations:
Preamplifiers: B&K 2673 and ZE0796 with shunt capacitance of 4.7466 nF
Plane wave couplers: CPL2898, CPL2888, CPL203 and CPL204 with needle bung DA5563 to seal
the couplers capilar pressure equalization vents
Microphone fixture: B&K 1412
Measurement frontend: Aurlio Audio CMF22 (with integrated switching facility for insert
voltage and mic-TX mode)
Measurement and analysis software: Monkey Forest
Statistical post-processing: Excel worksheets
The microphone fixture with the coupler and microphones inside was placed on a pneumatically
suspended table (Kinetic Systems) normally used by the Electroacoustic Laboratory in order to reduce
structure-borne infrasonic interference. The microphones front cavity depths were measured with a
microscope equipped with meter scale and the coupler lengths determined by means of a Carl Zeiss
UMM-500 precision coordinate measurement system.
Estimation of acoustic transfer impedances The total acoustic impedance of each setup consisting of two microphones in a coupler, needed in the relations of equation (7), was estimated by using equation (4) on page 11 of the standard [1]. This equation takes as input the individual acoustic admittances of the two microphones and the one of the coupler itself, connected by terms taken from transmission line theory to account for the idealized propagation of a supposed plane wave in the couplers. Estimation of acoustic microphone admittances To estimate the acoustic microphone admittances, nominal values for the resonance frequency (22 kHz), the equivalent volume (see table below) and the loss factor (1.07) were used to yield the lumped elements (acoustic mass, compliance and resistance, connected in series in the equivalent electric circuit) according to the three equations given in annex E of the standard [1]. To account for thermal losses via the diaphragm, an additional admittance defined in equation A.5 on page 22 was added to each acoustic microphone admittance. Estimation of the couplers acoustic impedances The acoustic impedance of each coupler, needed to feed equation (4) on page 11, was estimated by taking into account isothermal and viscous losses according to the broadband solution (A.3 on page 22), corresponding to operating Brel and Kjrs MP.EXE software in the IEC- mode. The ingredients for calculating the complex coupler impedance Za,0 along with the complex propagation
coefficient _ (i.e. sound velocity, viscosity, ratio of specific heats, density and thermal diffusivity of the
air enclosed in the coupler) were calculated according to the equation framework given in annex F. An
offset of +1.5 C was added to the laboratory temperature to estimate the temperature inside the
coupler, similar to what the software RMP.EXE (which controls the reciprocity apparatus 9699 in
traditional reciprocity calibration setups) does.
It was understood that the viscous and thermal losses contemplated by equations A.3 and A.4 are those
occurring along the total length of the inner cylindrical surface comprising the coupler volume and the
42
two microphone front cavities. The equations do not seem to contemplate the different thermal
conductivities of the shells, composed of different materials (sapphire vs. nickel alloy) with different
thicknesses.
The thermal losses occurring at the end surfaces (diaphragms) were accounted for separately by
equation A.5, defining an additional admittance to be added to the acoustic admittances of the
microphones..
Excitation and signal processing Instead of traditional pure tone testing, a broadband signal in conjunction with synchronous AD/DA conversion, FFT and deconvolution techniques was used to determine the complex electrical transfer functions between the transmitting and receiving microphones with high spectral resolution. The special excitation signal generated for this purpose, using the method described in chapter 4.3 of
reference [4], has a duration of 221 samples and was played back with a sample rate of 64 kHz,
corresponding to roughly 32.8 seconds. The figure 1 shows the spectrum of the excitation signal. It
features a spectral distribution adapted to the prevailing background noise to render the SNR of the
measurements almost frequency independent. The envelope of the amplitude is constant (4 Vrms). As
there is a strong emphasis for the subsonic frequencies at the inferior limit of the frequency range to be
reported, the excitation signal spends most of the time passing through these infrasonic frequencies.
Components that interfere in the determination of the sensitivity of the microphones, harmonic
distortion artifacts and background noise were later suppressed by windowing the impulse responses
correspondent to the measured transfer functions.
As shown in the block diagram of the Figure 2, the swept sine drives the transmitting microphone
preamplifier ZE0796 over a precision 10 k resistor (built-in the measurement frontend to maintain
compatibility with the B&K 5998 reciprocity apparatus concerning the frequency-dependant driving
voltage of the TX microphone).
43
The acoustic signal is converted into an electric signal by the receiver microphone and an analog-to-
digital converter (ADC) digitizes the electric signals. This way, the received signals can be processed
using the fast Fourier transform (FFT). A linear deconvolution has been used by padding the excitation
signal and the microphone preamplifier output signals with zeros to double the original length (Figure
2). The deconvolution is performed in the spectral domain via division of the response spectra by that of
the excitation signal. To achieve highest accuracy, the deconvolution spectrum would normally be
derived from a reference measurement in which the excitation signal is directly passed from the
measurement system's output to the input. This allows to eliminate any deviation from the ideal
frequency-independent gain of the measurement system's signal processing itself. However, this step
has been omitted here because the correction of the gain and phase deviations of the measurement
system channels occurs automatically by dividing the measured acoustical transfer functions by the
electrical transfer functions obtained with the voltage insertion technique. The voltage insertion takes
both the frequency response of the B&K preamplifiers (types ZE0796 and 2673) and the measurement
systems signal processing into account.
The voltage drop over the shunt capacitor in the ZE0796 preamplifier that drives the transmitter
microphone was measured simultaneously with the output voltage from the B&K 2673 preamplifier
attached to the receiving microphone. The relays for switching between voltage insertion (Lemo 1B pin
1) and transmit mode (Lemo 1B pin 5) are integrated in the measurement frontend and remote-
controllable from the measurement software.
The measurements of the electrical transfer impedances were accomplished with four different couplers
(Brel & Kjaer CPL2898, CPL2888, CPL203 and CPL204). The nominal volumes of the couplers are:
CPL2898 is 0.7cc, CPL2888 is 0.4cc, CPL203 is 0.2cc and CPL204 is 0.25cc.
The final transfer functions were obtained by executing FFTs over 1M samples only, resulting in a
frequency resolution of 30.519 mHz between the FFT bins. To obtain the values at the exact 10 base
fractional octave frequencies, a linear interpolation of the dB and phase values was performed between
the frequency bins adjacent to the required report frequency.
The microphone sensitivity (magnitude and phase) was calculated according to equation (7) on page 12
of the IEC61094-2:2009. The complex results were then adjusted to the reference environmental
conditions by using the tenth-order polynomial corrections given by Knud Rasmussen in reference [2],
44
As the measurements had been executed almost at sea level and very near to the reference
temperature of 23C, the corrections were almost insignificant (in the range of the uncertainty budget).
Six replicas were obtained during 6 different days and the arithmetic dB and phase average of them
constitutes the final result. The deviation from the ideal 180 phase shift expected at low frequencies
was mainly caused by the thermal loss corrections imposed by the IEC 61094-2:2009 standard.
The measuring system (Aurelio CMF22) used to measurement the electrical transfer impedance (Ze,xy) was conceived at the Acoustic and Vibration Division (DIAVI) of INMETRO. The software Monkey Forest controls the Aurelio CMF22 and now also performs the complete calculation and final export of the sensitivities of microphones. References [1]: IEC 61094-2:2009 Primary method for pressure calibration of laboratory standard microphones
by the reciprocity technique [2]: Knud Rasmussen, The Influence of Environmental Conditions on the Pressure Sensitivity of Measurement Microphones. Brel & Kjr Review 1, 2001, p. 1-13. [3]: Erling Frederiksen, Reduction of heat conduction error in microphone pressure reciprocity calibration. Brel & Kjr Review 1, 2001, p. 14-23. [4]: Swen Mller, Paulo Massarani, Transfer-function Measurements with Sweeps, Journal of the Audio Engineering Society 25,1037-1067 (2001)
45
B.4 KEBS
Method
The microphones were calibrated according to KEBS procedure QMET/15/CP/04. This procedure meets
the requirements of IEC 61094-2: 2009, in the determination of modulus of sensitivity of a LS2P
microphone. Phase measurements were not done.
The following equipment was used in the calibration process; Fluke 8508A Reference Multimeter S/No. 913152494 Brel and Kjr Signal Generator Type 1051 S/No. 2431664 Brel and Kjr Band Pass Filter Type 1617 S/No. 2514666
Brel and Kjr Reciprocity calibration apparatus Type 5998 S/No. 2545079 Brel and Kjr Plane wave coupler Type UA 1430 3888
Fluke 1620 Thermohygrometer S/No. 465117 GE Druck PACE 1000 Barometer S/No. 3722126 Polarisation voltage was 200.0 V 0.05 V
The voltage ratio measurements were carried out using the equipment above. Information from these
measurements including the static pressure, temperature and humidity, were then used by calculation
software MP.EXE version 4 to calculate the modulus of microphone sensitivity.
The front and equivalent volumes of the microphones were determined using curve fitting from the
results of two couplers, i.e. Brel and Kjr couplers UA1430 and UA1414 with nominal volumes 4 cm3
and 7 cm3 respectively.
Nominal values were used for the other microphone lump parameters.
Heat conduction correction was calculated according to the broad-band solution given in IEC 61094-2,
Annex A, clause A.3. This solution takes heat conduction and viscous losses into account by using
complex propagation coefficient and characteristic admittance in the transmission line theory used for
calculating the acoustic transfer admittance of the plane wave couplers.
The remaining heat conduction at the plane end surfaces, the two microphone diaphragms, is calculated
by adding an extra complex admittance term to the admittance of the diaphragms.
Radial wave motion correction was calculated for each combination of coupler and microphones
according to the theory and the equations given in Rasmussen 1993: Radial wave-motion in cyclindrical
plane-wave couplers, Acta Acustica, 1, pp 145-151 clause 5.3, assuming a Bessel distribution of the
diaphragm velocity distribution.
Capillary tube correction was calculated from the formulas in IEC 61094-2:2009 Annex B as a parallel
admittance to the closed coupler admittance.
The static pressure, temperature and humidity corrections were performed using the standard curve
feature of the calculation software MP.EXE. This utilises data in a resource file, normalized according to
the resonance frequency as regards the frequency dependence and with a typical value at 250 Hz
corresponding to the default microphone data. The actual values for the coefficients used are derived
46
from the normalized values using the actual resonance frequency of the microphone as given in the
microphone data file.
Finally the calculated sensitivities at mean environmental conditions were corrected to the sensitivities
at reference environmental conditions by applying the individual environmental coefficients for each
microphone.
The reference environmental conditions are:
Static pressure: 101.325 kPa; Temperature: 23.0 C Rel. humidity: 50 %.
47
B.5 METAS
Method
The primary calibration of the complex pressure sensitivity of LS1 and LS2 microphones at METAS is
based on the reciprocity technique according to the IEC 61094-2:2009 standard. METAS is using a
dedicated measurement setup involving hardware provided by different manufactureres. The LabView
software for the data acquisition as well as the Matlab-Scripts for the data analysis have been
developped in-house.
The microphone pairs are assembled in four different saphire couplers manufactured by METAS in
various lengths (for LS2 microphones between 3.06 mm and 6.10 mm). The complex electrical transfer
impedance is measured using a PXI-4461 data aquisition card by National Instruments. The current of
the microphone serving as transmitter is measured as a voltage drop on a reference capacitor (B&K ZE
0796). We are using the fixture B&K UA 1412 which may be hermetically sealed using a glas bell jar and
which is pressurized to 101.325 kPa using a manually operated bulb. The static pressure is read from a
Druck barometer DPI 141. B&K's reciprocity calibration apparatus type 5998 is used for the switching
(necessary for insert voltage measurements), for the signal conditioning and as the polarization source
of the microphones. The measurements are performed in an air conditioned yet silent lab (semi-
anechoic room) and the temperature of the room (as well as of the couplers used) is monitored
throughout the measurements. The data analysis is performed using a Matlab-program developped by
METAS. The microphone parameters (resonance frequency, equivalent volume as well as loss factor) are
determined by an iterative procedure involving data fitting aiming at minimizing the differencies of the
sensitivities obtained in the four couplers while taking into account the proportionality of the acoustic
admittance and the sensitivity.
48
B.6 NMISA
Method
The open-circuit pressure and phase sensitivities of the microphone were determined by the pressure
reciprocity technique as described in IEC 61094-2: 2009. A Brel & Kjr 9699 calibration system,
comprising of a 5998 reciprocity calibration apparatus with low frequency modification WH3432 and a
Pulse front-end 3560-C, was used in measuring the voltage ratios. The Pulse front-end was used in the
SSR mode with an accuracy setting of 0,001 dB and with generator levels of 2 V and 3 V, the latter being
for the low frequency range to improve signal-to-noise levels. Grounded guard configurations were used
for the transmitter unit, Brel & Kjr ZE-0796-W-001, and the two preamplifiers, Brel & Kjr 2673-W-
003 and 2673-W-004. The microphone measurement pairings were placed inside a chamber that
attenuates environmental noise and which was pressurised to the nominal reference static pressure.
Additionally, the chamber was placed on a static vibration isolation table.
The environmental parameters were measured using a Rotronics Hygroclip probe placed inside the
chamber and a Druck DPI141 barometer that measured the static pressure inside the chamber. The
microphones modulus and phase pressure- and temperature coefficients were determined based on
the technique as described by: K. Rasmussen, The static pressure and temperature coefficients of
laboratory standard microphones, Metrologia, 1999, 36, pp. 265 273; K. Rasmussen, The influence of
environmental conditions on the pressure sensitivity of measurement microphones, Brel and Kjr
Technical Review No. 1 2001.
The broad-band solution, as described in IEC 61094-2: 2009, was applied in correcting for heat
conduction effects together with corrections made for radial wave motion. Four air filled sapphire
plane-wave couplers of nominal lengths 3,06 mm, 3,75 mm, 4,70 mm and 6,10 mm were used. The two
couplers with the longest nominal lengths were used at the lowest frequencies and the two couplers
with the shortest nominal lengths were used at the highest frequencies. The results were calculated
with the Mp.exe V4.0 software.
The front volume, equivalent volume, resonant frequency and loss factor were determined by
employing analytical calculations, using the four plane-wave couplers.
The polarizing voltage was 200 Vdc 0,05 Vdc.
ANNEX C PARTICIPANT REPORTED RESULTS
C.1 DFM
Artefact
Frequency
(Hz)
Modulus
(dB re 1 V/Pa)
Modulus UoM
(dB)
Phase
()
Phase UoM
()
Modulus
(dB re 1 V/Pa)
Modulus UoM
(dB)
Phase
()
Phase UoM
()
1.000
1.259
1.5851.995 -37.372 0.130 176.48 0.31 -38.725 0.130 177.57 0.31
2.512 -37.439 0.130 176.98 0.31 -38.768 0.130 178.26 0.31
3.162 -37.499 0.130 177.38 0.31 -38.798 0.130 178.47 0.31
3.981 -37.552 0.120 177.59 0.23 -38.820 0.120 178.68 0.23
5.012 -37.598 0.120 177.82 0.23 -38.835 0.120 178.83 0.23
6.310 -37.637 0.120 178.07 0.23 -38.854 0.120 178.94 0.23
7.943 -37.671 0.110 178.24 0.20 -38.869 0.110 179.05 0.20
10.000 -37.703 0.110 178.41 0.20 -38.884 0.110 179.14 0.20
12.589 -37.732 0.110 178.56 0.20 -38.898 0.110 179.21 0.20
15.849 -37.756 0.100 178.70 0.16 -38.911 0.100 179.27 0.16
19.953 -37.778 0.100 178.82 0.16 -38.924 0.100 179.34 0.16
25.119 -37.797 0.080 178.94 0.16 -38.935 0.080 179.39 0.16
31.623 -37.814 0.080 179.03 0.14 -38.944 0.080 179.44 0.14
39.811 -37.828 0.080 179.11 0.14 -38.951 0.080 179.46 0.14
50.119 -37.840 0.080 179.17 0.14 -38.959 0.080 179.48 0.14
63.096 -37.852 0.040 179.21 0.08 -38.965 0.040 179.49 0.08
79.433 -37.861 0.040 179.23 0.08 -38.972 0.040 179.49 0.08
100.000 -37.870 0.040 179.23 0.08 -38.976 0.040 179.47 0.08
125.893 -37.878 0.030 179.21 0.06 -38.981 0.030 179.43 0.06
158.489 -37.885 0.030 179.17 0.06 -38.985 0.030 179.37 0.06
199.526 -37.890 0.030 179.09 0.06 -38.988 0.030 179.29 0.06
251.189 -37.896 0.030 178.98 0.06 -38.991 0.030 179.17 0.06
316.228 -37.901 0.030 178.84 0.06 -38.994 0.030 179.02 0.06
398.107 -37.905 0.030 178.63 0.06 -38.995 0.030 178.83 0.06
501.187 -37.908 0.030 178.37 0.06 -38.997 0.030 178.57 0.06
630.957 -37.910 0.030 178.03 0.06 -38.998 0.030 178.24 0.06
794.328 -37.911 0.030 177.58 0.06 -38.998 0.030 177.83 0.06
1 000.00 -37.911 0.030 177.02 0.06 -38.997 0.030 177.30 0.06
1 258.93 -37.908 0.030 176.30 0.09 -38.994 0.030 176.63 0.09
1 584.89 -37.902 0.030 175.39 0.09 -38.989 0.030 175.78 0.09
1 995.26 -37.890 0.030 174.23 0.09 -38.979 0.030 174.70 0.09
2 511.89 -37.869 0.030 172.75 0.09 -38.962 0.030 173.33 0.09
3 162.28 -37.836 0.030 170.86 0.09 -38.935 0.030 171.59 0.09
3 981.07 -37.783 0.030 168.40 0.09 -38.894 0.030 169.32 0.09
5 011.87 -37.702 0.030 165.19 0.13 -38.830 0.030 166.39 0.13
6 309.57 -37.579 0.030 160.90 0.13 -38.734 0.030 162.52 0.13
7 943.28 -37.407 0.030 155.00 0.15 -38.598 0.030 157.28 0.15
10 000.0 -37.198 0.030 146.58 0.17 -38.427 0.030 149.97 0.17
12 589.3 -37.067 0.040 134.28 0.20 -38.292 0.040 139.47 0.20
15 848.9 -37.377 0.050 116.44 0.23 -38.434 0.050 124.33 0.23
19 952.6 -38.852 0.080 94.34 0.53 -39.382 0.080 104.49 0.53
25 118.9 -41.799 0.100 74.26 0.62 -41.645 0.100 83.91 0.62
31 622.8 -45.430 0.170 61.19 1.42 -44.823 0.170 67.78 1.42
4180 s/n: 2049570 4180 s/n: 2787487
50
C.2 GUM
Artefact
Frequency
(Hz)
Modulus
(dB re 1 V/Pa)
Modulus UoM
(dB)
Phase
()
Phase UoM
()
Modulus
(dB re 1 V/Pa)
Modulus UoM
(dB)
Phase
()
Phase UoM
()
1.000
1.259
1.585
1.995
2.512
3.162
3.981
5.012
6.310
7.943
10.000
12.589
15.849
19.953 -37.80 0.07 179.01 1.7 -38.94 0.07 179.84 1.7
25.119 -37.81 0.06 179.13 1.3 -38.94 0.06 179.83 1.3
31.623 -37.83 0.05 179.20 1.1 -38.95 0.05 179.82 1.1
39.811 -37.84 0.05 179.28 1.1 -38.95 0.05 179.80 1.1
50.119 -37.84 0.05 179.33 1.1 -38.96 0.05 179.78 1.1
63.096 -37.86 0.05 179.36 0.8 -38.96 0.05 179.75 0.8
79.433 -37.86 0.05 179.38 0.8 -38.96 0.05 179.72 0.8
100.000 -37.87 0.05 179.37 0.8 -38.96 0.05 179.69 0.8
125.893 -37.88 0.04 179.33 0.6 -38.96 0.04 179.63 0.6
158.489 -37.88 0.04 179.28 0.6 -38.97 0.04 179.55 0.6
199.526 -37.88 0.04 179.20 0.6 -38.97 0.04 179.46 0.6
251.189 -37.89 0.04 179.08 0.5 -38.97 0.04 179.33 0.5
316.228 -37.89 0.04 178.93 0.5 -38.97 0.04 179.13 0.5
398.107 -37.90 0.04 178.71 0.5 -38.97 0.04 178.94 0.5
501.187 -37.90 0.03 178.45 0.5 -38.97 0.03 178.69 0.5
630.957 -37.90 0.03 178.12 0.5 -38.97 0.03 178.32 0.5
794.328 -37.90 0.03 177.59 0.5 -38.97 0.03 177.94 0.5
1 000.00 -37.90 0.03 177.12 0.4 -38.97 0.03 177.38 0.4
1 059.25 -37.90 0.03 176.95 0.4 -38.97 0.03 177.21 0.4
1 122.02 -37.90 0.03 176.70 0.4 -38.97 0.03 177.16 0.4
1 188.50 -37.90 0.03 176.62 0.4 -38.97 0.03 176.85 0.4
1 258.93 -37.89 0.03 176.40 0.4 -38.96 0.03 176.70 0.4
1 333.52 -37.89 0.03 176.13 0.4 -38.96 0.03 176.44 0.4
1 412.54 -37.89 0.03 175.92 0.4 -38.96 0.03 176.25 0.4
1 496.24 -37.89 0.03 175.71 0.4 -38.96 0.03 176.05 0.4
1 584.89 -37.89 0.03 175.46 0.4 -38.96 0.03 175.82 0.4
1 678.80 -37.88 0.03 175.20 0.4 -38.96 0.03 175.57 0.4
1 778.28 -37.88 0.03 174.92 0.4 -38.95 0.03 175.30 0.4
1 883.65 -37.88 0.03 174.62 0.4 -38.95 0.03 175.03 0.4
1 995.26 -37.88 0.03 174.31 0.4 -38.95 0.03 174.73 0.4
2 113.49 -37.87 0.03 173.98 0.4 -38.94 0.03 174.45 0.4
2 238.72 -37.86 0.03 173.64 0.4 -38.94 0.03 174.09 0.4
2 371.37 -37.86 0.03 173.23 0.4 -38.93 0.03 173.75 0.4
2 511.89 -37.85 0.03 172.85 0.4 -38.93 0.03 173.35 0.4
2 660.73 -37.84 0.03 172.38 0.4 -38.92 0.03 172.95 0.4
2 818.38 -37.84 0.03 171.93 0.4 -38.92 0.03 172.53 0.4
2 985.38 -37.83 0.03 171.42 0.4 -38.91 0.03 172.02 0.4
3 162.28 -37.81 0.03 170.92 0.4 -38.90 0.03 171.57 0.4
3 349.65 -37.80 0.03 170.36 0.4 -38.89 0.03 171.05 0.4
3 548.13 -37.79 0.03 169.76 0.4 -38.88 0.03 170.52 0.4
3 758.37 -37.78 0.03 169.14 0.4 -38.87 0.03 169.90 0.4
3 981.07 -37.76 0.03 168.48 0.5 -38.86 0.03 169.27 0.5
4 216.97 -37.75 0.03 167.73 0.5 -38.85 0.03 168.66 0.5
4 466.84 -37.72 0.03 166.95 0.5 -38.83 0.03 167.90 0.5
4 731.51 -37.70 0.03 166.12 0.5 -38.82 0.03 167.19 0.5
5 011.87 -37.68 0.03 165.26 0.5 -38.80 0.03 166.33 0.5
5 308.84 -37.65 0.03 164.29 0.5 -38.78 0.03 165.45 0.5
5 623.41 -37.62 0.03 163.30 0.5 -38.76 0.03 164.55 0.5
5 956.62 -37.59 0.03 162.14 0.5 -38.72 0.03 163.67 0.5
6 309.57 -37.56 0.04 160.97 0.5 -38.70 0.04 162.54 0.5
6 683.44 -37.52 0.04 159.74 0.5 -38.67 0.04 161.34 0.5
7 079.46 -37.47 0.04 158.34 0.5 -38.64 0.04 160.09 0.5
7 498.94 -37.43 0.04 156.80 0.5 -38.61 0.04 158.72 0.5
7 943.28 -37.38 0.05 155.15 0.6 -38.57 0.05 157.25 0.6
8 413.95 -37.33 0.05 153.34 0.6 -38.53 0.05 155.65 0.6
8 912.51 -37.28 0.05 151.35 0.6 -38.49 0.05 153.89 0.6
9 440.61 -37.23 0.05 149.13 0.6 -38.45 0.05 152.01 0.6
10 000.00 -37.17 0.06 146.73 0.7 -38.41 0.06 149.90 0.7
4180 s/n: 2049570 4180 s/n: 2787487
51
10 592.5 -37.13 0.06 144.06 0.7 -38.37 0.06 147.61 0.7
11 220.2 -37.09 0.06 141.12 0.7 -38.34 0.06 145.11 0.7
11 885.0 -37.06 0.06 137.89 0.7 -38.31 0.06 142.33 0.7
12 589.3 -37.05 0.08 134.34 0.7 -38.29 0.08 139.35 0.7
13 335.2 -37.07 0.08 130.42 0.7 -38.29 0.08 136.02 0.7
14 125.4 -37.12 0.08 126.13 0.7 -38.31 0.08 132.41 0.7
14 962.4 -37.22 0.08 121.51 0.7 -38.36 0.08 128.50 0.7
15 848.9 -37.38 0.08 116.49 0.9 -38.45 0.08 124.20 0.9
16 788.0 -37.61 0.08 111.19 0.9 -38.59 0.08 119.62 0.9
17 782.8 -37.94 0.08 105.63 0.9 -38.79 0.08 114.78 0.9
18 836.5 -38.37 0.08 99.92 0.9 -39.09 0.08 109.48 0.9
19 952.6 -38.90 0.12 94.27 1.3 -39.45 0.12 104.15 1.3
21 134.9 -39.53 0.12 88.64 1.3 -39.91 0.12 98.57 1.3
22 387.2 -40.28 0.12 83.35 1.3 -40.48 0.12 93.41 1.3
23 713.7 -41.09 0.12 78.46 1.3 -41.10 0.12 88.22 1.3
25 118.9 -41.96 0.24 74.03 1.9 -41.81 0.24 83.27 1.9
26 607.3
28 183.8
29 853.8
31 622.8
52
C.3 INMETRO
Artefact
Frequency
(Hz)
Modulus
(dB re 1 V/Pa)
Modulus UoM
(dB)
Phase
()
Phase UoM
()
Modulus
(dB re 1 V/Pa)
Modulus UoM
(dB)
Phase
()
Phase UoM
()
1.00 -37.457 0.310 176.076 4.80 -38.776 0.310 176.751 4.80
1.06 -37.409 0.290 175.689 4.70 -38.758 0.290 176.609 4.70
1.12 -37.377 0.270 175.545 4.60 -38.751 0.270 176.762 4.60
1.19 -37.382 0.260 175.454 4.60 -38.761 0.260 176.618 4.60
1.26 -37.423 0.250 175.740 4.60 -38.780 0.250 176.487 4.60
1.33 -37.455 0.240 175.975 4.40 -38.784 0.240 176.754 4.40
1.41 -37.442 0.230 176.610 4.30 -38.758 0.230 177.086 4.30
1.50 -37.417 0.220 176.490 4.20 -38.741 0.220 177.192 4.20
1.58 -37.387 0.210 176.651 4.10 -38.733 0.210 177.134 4.10
1.68 -37.381 0.200 176.535 4.00 -38.754 0.200 177.056 4.00
1.78 -37.396 0.200 176.569 3.80 -38.786 0.200 177.091 3.80
1.88 -37.444 0.200 176.575 3.70 -38.816 0.200 177.337 3.70
2.00 -37.470 0.200 176.910 3.60 -38.806 0.200 177.604 3.60
2.11 -37.443 0.190 176.898 3.20 -38.767 0.190 177.573 3.20
2.24 -37.438 0.190 176.956 3.00 -38.792 0.190 177.475 3.00
2.37 -37.471 0.180 177.053 2.70 -38.856 0.180 177.768 2.70
2.51 -37.457 0.170 177.123 2.50 -38.822 0.170 178.138 2.50
2.66 -37.478 0.170 176.940 2.20 -38.797 0.170 177.877 2.20
2.82 -37.523 0.160 177.163 2.15 -38.824 0.160 177.916 2.15
2.99 -37.510 0.160 177.292 2.10 -38.807 0.160 178.321 2.10
3.16 -37.532 0.150 177.275 2.00 -38.826 0.150 178.295 2.00
3.35 -37.538 0.150 177.416 1.80 -38.823 0.150 178.403 1.80
3.55 -37.557 0.140 177.407 1.60 -38.810 0.140 178.470 1.60
3.76 -37.564 0.140 177.587 1.30 -38.823 0.140 178.454 1.30
3.98 -37.572 0.130 177.586 1.25 -38.832 0.130 178.582 1.25
4.22 -37.581 0.130 177.678 1.20 -38.821 0.130 178.609 1.20
4.47 -37.594 0.130 177.714 1.15 -38.831 0.130 178.601 1.15
4.73 -37.596 0.130 177.770 1.10 -38.823 0.130 178.705 1.10
5.01 -37.616 0.130 177.801 1.10 -38.838 0.130 178.693 1.10
5.31 -37.634 0.120 177.876 1.00 -38.824 0.120 178.669 1.00
5.62 -37.627 0.110 178.016 0.98 -38.833 0.110 178.801 0.98
5.96 -37.642 0.100 178.030 0.96 -38.838 0.100 178.801 0.96
6.31 -37.643 0.090 178.135 0.95 -38.839 0.090 178.773 0.95
6.68 -37.661 0.090 178.189 0.94 -38.829 0.090 178.875 0.94
7.08 -37.654 0.090 178.154 0.92 -38.860 0.090 178.776 0.92
7.50 -37.664 0.090 178.159 0.91 -38.853 0.090 179.112 0.91
7.94 -37.679 0.080 178.327 0.90 -38.815 0.080 178.878 0.90
8.41 -37.698 0.080 178.252 0.87 -38.842 0.080 179.068 0.87
8.91 -37.706 0.070 178.381 0.85 -38.866 0.070 179.173 0.85
9.44 -37.687 0.070 178.486 0.73 -38.852 0.070 179.050 0.73
10.00 -37.702 0.060 178.405 0.80 -38.852 0.060 179.169 0.80
10.59 -37.711 0.060 178.435 0.77 -38.872 0.060 179.103 0.77
11.22 -37.709 0.060 178.589 0.75 -38.873 0.060 179.123 0.75
11.89 -37.728 0.060 178.543 0.70 -38.871 0.060 179.197 0.70
12.59 -37.732 0.060 178.634 0.60 -38.869 0.060 179.250 0.60
13.34 -37.746 0.050 178.666 0.57 -38.870 0.050 179.244 0.57
14.13 -37.736 0.05 178.719 0.55 -38.883 0.050 179.263 0.55
14.96 -37.750 0.05 178.748 0.53 -38.883 0.050 179.305 0.53
15.85 -37.758 0.05 178.784 0.50 -38.886 0.050 179.410 0.50
16.79 -37.761 0.05 178.812 0.45 -38.888 0.050 179.278 0.45
17.78 -37.764 0.05 178.866 0.40 -38.892 0.050 179.447 0.40
18.84 -37.771 0.05 178.950 0.35 -38.894 0.050 179.457 0.35
19.95 -37.776 0.05 178.958 0.30 -38.889 0.050 179.417 0.30
21.13 -37.776 0.045 178.925 0.30 -38.889 0.045 179.502 0.30
22.39 -37.788 0.045 179.003 0.20 -38.895 0.045 179.503 0.20
23.71 -37.787 0.045 179.000 0.30 -38.891 0.045 179.497 0.30
25.12 -37.785 0.045 179.027 0.30 -38.899 0.045 179.542 0.30
26.61 -37.790 0.045 179.036 0.30 -38.901 0.045 179.545 0.30
28.18 -37.798 0.045 179.091 0.30 -38.900 0.045 179.532 0.30
29.85 -37.800 0.045 179.101 0.30 -38.901 0.045 179.566 0.30
31.62 -37.807 0.045 179.114 0.30 -38.898 0.045 179.561 0.30
33.50 -37.807 0.045 179.120 0.30 -38.902 0.045 179.573 0.30
35.48 -37.813 0.045 179.179 0.30 -38.902 0.045 179.572 0.30
37.58 -37.808 0.045 179.195 0.30 -38.909 0.045 179.541 0.30
39.81 -37.811 0.045 179.173 0.30 -38.910 0.045 179.608 0.30
42.17 -37.814 0.045 179.202 0.30 -38.907 0.045 179.624 0.30
44.67 -37.818 0.045 179.192 0.30 -38.909 0.045 179.572 0.30
47.32 -37.821 0.045 179.224 0.30 -38.910 0.045 179.595 0.30
50.12 -37.826 0.045 179.256 0.30 -38.909 0.045 179.590 0.30
53.09 -37.824 0.045 179.243 0.30 -38.913 0.045 179.606 0.30
56.23 -37.832 0.045 179.246 0.30 -38.911 0.045 179.603 0.30
59.57 -37.829 0.045 179.260 0.30 -38.914 0.045 179.585 0.30
63.10 -37.830 0.045 179.283 0.30 -38.914 0.045 179.583 0.30
4180 s/n: 2049570 4180 s/n: 2787487
53
66.83 -37.832 0.045 179.286 0.30 -38.918 0.045 179.597 0.30
70.79 -37.837 0.045 179.284 0.30 -38.917 0.045 179.581 0.30
74.99 -37.839 0.045 179.348 0.30 -38.919 0.045 179.583 0.30
79.43 -37.837 0.045 179.341 0.30 -38.917 0.045 179.560 0.30
84.14 -37.843 0.045 179.336 0.30 -38.918 0.045 179.547 0.30
89.13 -37.845 0.045 179.329 0.30 -38.921 0.045 179.549 0.30
94.41 -37.847 0.045 179.318 0.20 -38.919 0.045 179.527 0.20
100.00 -37.847 0.045 179.324 0.30 -38.922 0.045 179.502 0.30
105.93 -37.850 0.045 179.316 0.30 -38.925 0.045 179.565 0.30
112.20 -37.849 0.045 179.324 0.30 -38.925 0.045 179.518 0.30
118.85 -37.854 0.045 179.291 0.30 -38.926 0.045 179.510 0.30
125.89 -37.852 0.045 179.276 0.30 -38.927 0.045 179.493 0.30
133.35 -37.855 0.045 179.278 0.30 -38.929 0.045 179.513 0.30
141.25 -37.856 0.045 179.242 0.30 -38.925 0.045 179.506 0.30
149.62 -37.858 0.045 179.234 0.30 -38.928 0.045 179.470 0.30
158.49 -37.859 0.045 179.374 0.30 -38.930 0.045 179.440 0.30
167.88 -37.862 0.045 179.331 0.30 -38.931 0.045 179.407 0.30
177.83 -37.863 0.045 179.318 0.30 -38.931 0.045 179.361 0.30
188.37 -37.865 0.045 179.274 0.30 -38.933 0.045 179.495 0.30
199.53 -37.865 0.045 179.285 0.30 -38.934 0.045 179.448 0.30
211.35 -37.869 0.045 179.435 0.30 -38.934 0.045 179.576 0.30
223.87 -37.869 0.045 179.389 0.30 -38.935 0.045 179.581 0.30
237.14 -37.871 0.045 179.348 0.30 -38.934 0.045 179.531 0.30
251.19 -37.872 0.045 179.297 0.30 -38.935 0.045 179.481 0.30
266.07 -37.872 0.045 179.252 0.30 -38.935 0.045 179.490 0.30
281.84 -37.874 0.045 179.203 0.30 -38.936 0.045 179.435 0.30
298.54 -37.874 0.045 179.200 0.30 -38.936 0.045 179.378 0.30
316.23 -37.875 0.045 179.138 0.30 -38.938 0.045 179.370 0.30
334.97 -37.876 0.045 179.077 0.30 -38.937 0.045 179.308 0.30
354.81 -37.878 0.045 179.016 0.30 -38.937 0.045 179.238 0.30
375.84 -37.879 0.045 178.946 0.30 -38.938 0.045 179.168 0.30
398.11 -37.879 0.045 178.877 0.30 -38.938 0.045 179.095 0.30
421.70 -37.880 0.045 178.802 0.30 -38.938 0.045 179.020 0.30
446.68 -37.881 0.045 178.724 0.30 -38.939 0.045 178.953 0.30
473.15 -37.881 0.045 178.644 0.30 -38.939 0.045 178.866 0.30
501.19 -37.882 0.045 178.559 0.20 -38.939 0.045 178.784 0.20
530.88 -37.882 0.045 178.476 0.30 -38.940 0.045 178.721 0.30
562.34 -37.882 0.045 178.378 0.30 -38.941 0.045 178.628 0.30
595.66 -37.884 0.045 178.282 0.30 -38.940 0.045 178.528 0.30
630.96 -37.884 0.045 178.179 0.30 -38.939 0.045 178.433 0.30
668.34 -37.884 0.045 178.074 0.30 -38.939 0.045 178.325 0.30
707.95 -37.885 0.045 177.959 0.30 -38.940 0.045 178.200 0.30
749.89 -37.885 0.045 177.831 0.30 -38.939 0.045 178.085 0.30
794.33 -37.885 0.045 177.698 0.30 -38.941 0.045 177.978 0.30
841.40 -37.885 0.045 177.827 0.30 -38.941 0.045 177.854 0.30
891.25 -37.885 0.045 177.669 0.30 -38.940 0.045 177.716 0.30
944.06 -37.885 0.045 177.563 0.30 -38.940 0.045 177.567 0.30
1000.00 -37.885 0.045 177.374 0.30 -38.940 0.045 177.414 0.30
1059.25 -37.883 0.045 177.197 0.30 -38.938 0.045 177.251 0.30
1122.02 -37.883 0.045 177.004 0.30 -38.938 0.045 177.079 0.30
1188.50 -37.882 0.045 176.803 0.30 -38.937 0.045 176.895 0.30
1258.93 -37.881 0.045 176.589 0.30 -38.936 0.045 176.702 0.30
1333.52 -37.880 0.045 176.360 0.30 -38.934 0.045 176.507 0.30
1412.54 -37.879 0.045 176.125 0.30 -38.935 0.045 176.290 0.30
1496.24 -37.877 0.045 175.879 0.30 -38.932 0.045 176.059 0.30
1584.89 -37.875 0.045 175.615 0.30 -38.931 0.045 175.825 0.30
1678.80 -37.872 0.045 175.342 0.30 -38.929 0.045 175.571 0.30
1778.28 -37.869 0.045 175.044 0.30 -38.927 0.045 175.304 0.30
1883.65 -37.866 0.045 174.734 0.30 -38.925 0.045 175.019 0.30
1995.26 -37.862 0.045 174.407 0.30 -38.921 0.045 174.714 0.30
2113.49 -37.857 0.045 174.115 0.30 -38.918 0.045 174.415 0.30
2238.72 -37.853 0.045 173.743 0.30 -38.914 0.045 174.073 0.30
2371.37 -37.848 0.045 173.352 0.30 -38.911 0.045 173.712 0.30
2511.89 -37.842 0.045 172.934 0.30 -38.906 0.045 173.331 0.30
2660.73 -37.834 0.045 172.500 0.30 -38.901 0.045 172.931 0.30
2818.38 -37.826 0.045 172.026 0.20 -38.894 0.045 172.494 0.20
2985.38 -37.818 0.045 171.523 0.30 -38.887 0.045 172.031 0.30
3162.28 -37.808 0.045 170.992 0.30 -38.881 0.045 171.545 0.30
3349.65 -37.797 0.045 170.426 0.30 -38.873 0.045 171.023 0.30
3548.13 -37.785 0.045 169.826 0.30 -38.864 0.045 170.474 0.30
3758.37 -37.772 0.045 169.187 0.30 -38.854 0.045 169.886 0.30
3981.07 -37.757 0.045 168.503 0.30 -38.843 0.045 169.257 0.30
4216.97 -37.740 0.045 167.775 0.30 -38.830 0.045 168.588 0.30
4466.84 -37.720 0.045 166.993 0.30 -38.816 0.045 167.881 0.30
4731.51 -37.699 0.045 166.158 0.30 -38.799 0.045 167.114 0.30
5011.87 -37.676 0.045 165.255 0.30 -38.783 0.045 166.295 0.30
54
5308.84 -37.650 0.045 164.293 0.30 -38.763 0.045 165.418 0.30
5623.41 -37.621 0.045 163.258 0.30 -38.742 0.045 164.476 0.30
5956.62 -37.590 0.045 162.139 0.30 -38.719 0.045 163.467 0.30
6309.57 -37.556 0.045 160.933 0.30 -38.694 0.045 162.382 0.30
6683.44 -37.519 0.045 159.632 0.30 -38.666 0.045 161.215 0.30
7079.46 -37.479 0.045 158.216 0.30 -38.637 0.045 159.954 0.30
7498.94 -37.435 0.045 156.684 0.30 -38.604 0.045 158.588 0.30
7943.28 -37.390 0.045 155.016 0.30 -38.570 0.045 157.115 0.30
8413.95 -37.341 0.045 153.192 0.32 -38.534 0.045 155.511 0.32
8912.51 -37.291 0.045 151.202 0.33 -38.496 0.045 153.770 0.33
9440.61 -37.240 0.045 149.015 0.34 -38.457 0.045 151.868 0.34
10000.00 -37.190 0.045 146.619 0.35 -38.419 0.045 149.799 0.35
10592.50 -37.144 0.045 143.977 0.35 -38.381 0.045 147.531 0.35
11220.20 -37.103 0.045 141.053 0.35 -38.347 0.045 145.034 0.35
11885.00 -37.077 0.045 137.838 0.35 -38.322 0.045 142.307 0.35
12589.30 -37.070 0.045 134.313 0.35 -38.308 0.045 139.325 0.35
13335.20 -37.084 0.05 130.432 0.35 -38.306 0.050 136.051 0.35
14125.40 -37.135 0.05 126.185 0.40 -38.327 0.050 132.470 0.40
14962.40 -37.233 0.05 121.576 0.45 -38.377 0.050 128.566 0.45
15848.90 -37.391 0.05 116.611 0.50 -38.465 0.050 124.324 0.50
16788.00 -37.625 0.06 111.344 0.60 -38.604 0.060 119.759 0.60
17782.80 -37.945 0.07 105.859 0.70 -38.805 0.070 114.896 0.70
18836.50 -38.361 0.08 100.259 0.75 -39.078 0.080 109.790 0.75
19952.60 -38.878 0.09 94.670 0.80 -39.435 0.090 104.521 0.80
21134.90 -39.491 0.11 89.233 1.50 -39.877 0.110 99.161 1.50
22387.20 -40.191 0.13 84.066 1.70 -40.434 0.130 93.898 1.70
23713.70 -40.984 0.15 79.214 2.00 -41.049 0.150 88.740 2.00
25118.90 -41.821 0.16 74.842 2.20 -41.755 0.160 83.868 2.20
26607.30 -42.700 0.19 70.942 2.70 -42.514 0.190 79.323 2.70
28183.80 -43.572 0.23 67.528 3.00 -43.301 0.230 75.084 3.00
29853.80 -44.322 0.25 63.969 4.00 -44.003 0.250 70.512 4.00
31622.80 -46.660 0.27 50.141 4.70 -46.470 0.270 58.927 4.70
55
C.4 KEBS
Artefact
Frequency
(Hz)
Modulus
(dB re 1 V/Pa)
Modulus UoM
(dB)
Phase
()
Phase UoM
()
Modulus
(dB re 1 V/Pa)
Modulus UoM
(dB)
Phase
()
Phase UoM
()
1.000 - - - - - - - -
1.259 - - - - - - - -
1.585 - - - - - - - -
1.995 - - - - - - - -
2.512 - - - - - - - -
3.162 - - - - - - - -
3.981 - - - - - - - -
5.012 - - - - - - - -
6.310 - - - - - - - -
7.943 - - - - - - - -
10.000 -37.741 0.070 - - -38.896 0.070 - -
12.589 -37.767 0.070 - - -38.907 0.070 - -
15.849 -37.782 0.070 - - -38.918 0.070 - -
19.953 -37.802 0.070 - - -38.928 0.070 - -
25.119 -37.817 0.070 - - -38.938 0.070 - -
31.623 -37.831 0.070 - - -38.945 0.070 - -
39.811 -37.842 0.040 - - -38.953 0.040 - -
50.119 -37.854 0.040 - - -38.958 0.040 - -
63.096 -37.863 0.040 - - -38.964 0.040 - -
79.433 -37.871 0.040 - - -38.968 0.040 - -
100.000 -37.878 0.040 - - -38.973 0.040 - -
125.893 -37.886 0.040 - - -38.977 0.040 - -
158.489 -37.892 0.040 - - -38.979 0.040 - -
199.526 -37.897 0.040 - - -38.983 0.040 - -
251.189 -37.903 0.040 - - -38.986 0.040 - -
316.228 -37.908 0.040 - - -38.987 0.040 - -
398.107 -37.912 0.040 - - -38.990 0.040 - -
501.187 -37.915 0.040 - - -38.992 0.040 - -
630.957 -37.918 0.040 - - -38.993 0.040 - -
794.328 -37.920 0.040 - - -38.995 0.040 - -
1 000.00 -37.920 0.040 - - -38.995 0.040 - -
1 258.93 -37.918 0.040 - - -38.993 0.040 - -
1 584.89 -37.910 0.040 - - -38.986 0.040 - -
1 995.26 -37.897 0.040 - - -38.975 0.040 - -
2 511.89 -37.875 0.040 - - -38.957 0.040 - -
3 162.28 -37.840 0.040 - - -38.929 0.040 - -
3 981.07 -37.789 0.040 - - -38.890 0.040 - -
5 011.87 -37.708 0.040 - - -38.829 0.040 - -
6 309.57 -37.587 0.040 - - -38.737 0.040 - -
7 943.28 -37.411 0.040 - - -38.605 0.040 - -
10 000.0 -37.197 0.070 - - -38.435 0.070 - -
12 589.3 -37.074 0.070 - - -38.310 0.070 - -
15 848.9 -37.430 0.070 - - -38.511 0.070 - -
19 952.6 -38.886 0.260 - - -39.714 0.260 - -
25 118.9 -41.965 0.260 - - -41.964 0.260 - -
- - - - - - - - -
4180 s/n: 2049570 4180 s/n: 2787487
56
C.5 METAS
Artefact
Frequency
(Hz)
Modulus
(dB re 1 V/Pa)
Modulus UoM
(dB)
Phase
()
Phase UoM
()
Modulus
(dB re 1 V/Pa)
Modulus UoM
(dB)
Phase
()
Phase UoM
()
1.000 -37.097 0.500 176.07 4.00 -38.461 0.500 179.65 4.00
1.259 -37.177 0.300 176.41 4.00 -38.538 0.300 178.89 4.00
1.585 -37.271 0.280 176.55 4.00 -38.637 0.280 179.14 4.00
1.995 -37.371 0.280 176.81 2.34 -38.745 0.280 179.16 2.34
2.512 -37.458 0.280 177.21 2.34 -38.766 0.280 179.18 2.34
3.162 -37.517 0.280 177.50 2.34 -38.795 0.280 179.31 2.34
3.981 -37.559 0.280 177.69 2.34 -38.801 0.280 179.38 2.34
5.012 -37.606 0.130 177.98 0.78 -38.812 0.130 179.42 0.78
6.310 -37.635 0.130 178.15 0.78 -38.820 0.130 179.48 0.78
7.943 -37.669 0.130 178.35 0.78 -38.831 0.130 179.49 0.78
10.000 -37.698 0.130 178.50 0.78 -38.842 0.130 179.49 0.78
12.589 -37.724 0.090 178.64 0.32 -38.853 0.090 179.50 0.32
15.849 -37.748 0.090 178.77 0.32 -38.865 0.090 179.51 0.32
19.953 -37.770 0.090 178.89 0.32 -38.876 0.090 179.53 0.32
25.119 -37.788 0.060 178.99 0.16 -38.885 0.060 179.55 0.16
31.623 -37.803 0.060 179.08 0.16 -38.893 0.060 179.57 0.16
39.811 -37.816 0.060 179.15 0.16 -38.900 0.060 179.58 0.16
50.119 -37.828 0.034 179.20 0.08 -38.906 0.034 179.59 0.08
63.096 -37.839 0.034 179.24 0.08 -38.912 0.034 179.57 0.08
79.433 -37.848 0.034 179.26 0.08 -38.916 0.034 179.56 0.08
100.000 -37.857 0.034 179.25 0.08 -38.920 0.034 179.52 0.08
125.893 -37.864 0.034 179.23 0.08 -38.925 0.034 179.48 0.08
158.489 -37.871 0.034 179.19 0.08 -38.928 0.034 179.41 0.08
199.526 -37.877 0.034 179.11 0.08 -38.931 0.034 179.32 0.08
251.189 -37.882 0.034 179.00 0.08 -38.934 0.034 179.20 0.08
316.228 -37.887 0.034 178.84 0.08 -38.936 0.034 179.04 0.08
398.107 -37.891 0.034 178.64 0.08 -38.938 0.034 178.83 0.08
501.187 -37.894 0.034 178.37 0.08 -38.940 0.034 178.57 0.08
630.957 -37.896 0.034 178.03 0.08 -38.940 0.034 178.24 0.08
794.328 -37.897 0.034 177.59 0.08 -38.940 0.034 177.82 0.08
1 000.00 -37.897 0.035 177.02 0.08 -38.939 0.035 177.28 0.08
1 258.93 -37.894 0.035 176.30 0.09 -38.936 0.035 176.60 0.09
1 584.89 -37.887 0.035 175.39 0.09 -38.931 0.035 175.74 0.09
1 995.26 -37.875 0.035 174.22 0.09 -38.921 0.035 174.65 0.09
2 511.89 -37.855 0.035 172.74 0.09 -38.906 0.035 173.26 0.09
3 162.28 -37.821 0.035 170.84 0.09 -38.880 0.035 171.49 0.09
3 981.07 -37.768 0.035 168.38 0.09 -38.839 0.035 169.22 0.09
5 011.87 -37.684 0.043 165.16 0.09 -38.777 0.043 166.26 0.09
6 309.57 -37.561 0.043 160.84 0.14 -38.684 0.043 162.35 0.14
7 943.28 -37.387 0.043 154.91 0.14 -38.554 0.043 157.07 0.14
10 000.0 -37.177 0.097 146.48 0.48 -38.391 0.097 149.72 0.48
12 589.3 -37.039 0.097 134.05 0.48 -38.263 0.097 139.16 0.48
15 848.9 -37.330 0.097 116.17 0.48 -38.396 0.097 123.98 0.48
19 952.6 -38.792 0.189 93.64 1.93 -39.365 0.189 103.82 1.93
25 118.9 -41.902 0.326 72.47 2.02 -41.760 0.326 81.14 2.02
31 622.8 -45.806 0.326 60.328 2.020 -45.511 0.326 65.944 2.020
4180 s/n: 2049570 4180 s/n: 2787487
57
C.6 NMISA
Artefact
Frequency
(Hz)
Modulus
(dB re 1 V/Pa)
Modulus UoM
(dB)
Phase
()
Phase UoM
()
Modulus
(dB re 1 V/Pa)
Modulus UoM
(dB)
Phase
()
Phase UoM
()
1.000 -37.112 0.20 175.93 2.00 -38.477 0.20 177.01 2.00
1.259 -37.217 0.20 176.23 2.00 -38.585 0.20 177.26 2.00
1.585 -37.303 0.20 176.54 2.00 -38.665 0.20 177.58 2.00
1.995 -37.377 0.20 176.84 2.00 -38.723 0.20 177.94 2.00
2.512 -37.441 0.15 177.11 1.00 -38.761 0.15 178.25 1.00
3.162 -37.498 0.15 177.36 1.00 -38.787 0.15 178.50 1.00
3.981 -37.552 0.15 177.61 1.00 -38.806 0.15 178.70 1.00
5.012 -37.596 0.08 177.83 0.90 -38.824 0.08 178.85 0.90
6.310 -37.637 0.08 178.04 0.80 -38.840 0.08 178.97 0.80
7.943 -37.672 0.08 178.24 0.65 -38.855 0.08 179.07 0.65
10.000 -37.703 0.08 178.40 0.50 -38.870 0.08 179.15 0.50
12.589 -37.731 0.08 178.56 0.45 -38.884 0.08 179.22 0.45
15.849 -37.756 0.05 178.70 0.40 -38.897 0.05 179.28 0.40
19.953 -37.776 0.05 178.82 0.40 -38.907 0.05 179.34 0.40
25.119 -37.796 0.05 178.93 0.35 -38.917 0.05 179.40 0.35
31.623 -37.813 0.05 179.03 0.30 -38.927 0.05 179.44 0.30
39.811 -37.826 0.05 179.11 0.25 -38.935 0.05 179.47 0.25
50.119 -37.839 0.03 179.17 0.25 -38.942 0.03 179.49 0.25
63.096 -37.850 0.03 179.21 0.15 -38.948 0.03 179.50 0.15
79.433 -37.860 0.03 179.23 0.15 -38.954 0.03 179.49 0.15
100.000 -37.867 0.03 179.22 0.15 -38.958 0.03 179.46 0.15
125.893 -37.876 0.03 179.20 0.15 -38.962 0.03 179.43 0.15
158.489 -37.882 0.03 179.16 0.10 -38.966 0.03 179.37 0.10
199.526 -37.889 0.03 179.09 0.10 -38.970 0.03 179.28 0.10
251.189 -37.894 0.03 178.98 0.10 -38.972 0.03 179.17 0.10
316.228 -37.898 0.03 178.83 0.10 -38.975 0.03 179.02 0.10
398.107 -37.903 0.03 178.64 0.10 -38.977 0.03 178.83 0.10
501.187 -37.906 0.03 178.37 0.10 -38.979 0.03 178.57 0.10
630.957 -37.908 0.03 178.03 0.10 -38.980 0.03 178.25 0.10
794.328 -37.909 0.03 177.60 0.10 -38.980 0.03 177.84 0.10
1 000.00 -37.909 0.03 177.04 0.10 -38.979 0.03 177.31 0.10
1 258.93 -37.905 0.03 176.32 0.10 -38.975 0.03 176.65 0.10
1 584.89 -37.899 0.03 175.42 0.10 -38.970 0.03 175.80 0.10
1 995.26 -37.886 0.03 174.26 0.10 -38.959 0.03 174.73 0.10
2 511.89 -37.865 0.03 172.79 0.10 -38.943 0.03 173.36 0.10
3 162.28 -37.831 0.03 170.90 0.10 -38.916 0.03 171.61 0.10
3 981.07 -37.777 0.03 168.46 0.10 -38.875 0.03 169.37 0.10
5 011.87 -37.693 0.03 165.25 0.15 -38.810 0.03 166.45 0.15
6 309.57 -37.568 0.03 160.97 0.15 -38.713 0.03 162.59 0.15
7 943.28 -37.390 0.04 155.07 0.15 -38.577 0.04 157.36 0.15
10 000.0 -37.176 0.04 146.65 0.20 -38.406 0.04 150.05 0.20
12 589.3 -37.035 0.04 134.28 0.25 -38.266 0.04 139.52 0.25
15 848.9 -37.345 0.06 116.44 0.35 -38.399 0.06 124.27 0.35
19 952.6 -38.801 0.10 94.43 0.45 -39.383 0.10 104.15 0.45
25 118.9 -41.803 0.15 74.32 0.55 -41.775 0.15 83.56 0.55
31 622.8 -45.334 0.20 62.09 0.85 -45.145 0.20 68.62 0.85
4180 s/n: 2049570 4180 s/n: 2787487
ANNEX D PARTICIPANT UNCERTAINTIES
D.1 DFM
The condensed uncertainty budget for a pressure reciprocity calibration of LS2 microphones equivalent
to Brel & Kjr Type 4180 is given in the tables below. The background for the budget is as follows:
Front volume and Equivalent volume. The sum of the front volume and the equivalent volume of the
microphone are determined by fitting the sensitivity below half the resonance frequency obtained from
measurements in four couplers. The equivalent volume is then determined from the fitting of the
sensitivity at frequencies around and above the resonance frequency, keeping the total volume
unchanged.
Resonance frequency. A first approximation to the value of the resonance frequency can be made using
an empirical expression with an uncertainty of about 400 Hz. However, a more precise estimate is
obtained by determining the 90 degree phase shift in the sensitivity.
Loss factor. Obtained from the fitting of the sensitivity determined in four different couplers at
frequencies between half the resonance frequency and the resonance frequency.
Static pressure and temperature coefficients. The pressure coefficient can be determined using an
empirical equation. This value has an expanded uncertainty (k=2) of 0.0005 dB/Pa. There is not any
similar expression for the temperature coefficient, hence a typical value is used.
Cavity depth. This quantity has been measured using a laser based distance measurement system.
Coupler geometry. The length and the internal diameter of the couplers are calibrated using a
coordinate machine at an external calibration site.
Static pressure. The static pressure is measured before and after the transfer impedance (voltage ratio).
The static pressure is measured using a calibrated barometer. Provisions are taken to introduce the slow
variation of pressure during a measurement.
Temperature and Relative Humidity. These two quantities are measured in a similar way to the static
pressure. The quantities are measured using a Temperature/Relative Humidity probe. Slow changes in
relative humidity and temperature are also taken into account.
Reference capacitance and parallel resistance. The reference capacitance included in the transmitter
unit is calibrated with an uncertainty that has a frequency dependence. The resistance is determined
from measurements of the dissipation factor.
Complex ratio of voltages. The different voltages (output voltage on the receiver microphone, voltage
on the terminals of the reference impedance, and insert voltages) are measured using a PULSE analyser
with the Steady State Response (SSR) modality. The phase of the complex ratio is determined from the
differences among the four voltages measured. This implies that any difference between 3 channels will
be duly eliminated leaving only the uncertainty of the absolute phase provided from the verification of
the analyser.
59
Polarisation voltage. The polarisation voltage is provided by a DC Voltage calibrator. The supplied
voltage is monitored using a 8 digits DMM.
Rounding. Typically, sensitivity level results are rounded to the hundredth of a dB, and this introduces
an additional uncertainty component.
Allowable reproducibility. This component represents the maximum allowed reproducibility for any item
of the same characteristics as the LS2 microphone, and it is the contribution of the microphone under
calibration.
60
61
62
D.2 GUM
63
64
D.3 INMETRO
65
66
D.4 KEBS
67
D.5 METAS
Un
cert
ain
ty c
om
po
ne
nts
fo
r av
era
ge s
en
siti
vity
[d
B]
rela
tive
abso
lute
24.9
510
>10.
.10.
.