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)

2

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.

6

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.

7

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.

8

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.

9

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.

10

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.

11

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.

12

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.

13

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

16

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.

17

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.

19

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

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ain

ty c

om

po

ne

nts

fo

r av

era

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en

siti

vity

[d

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rela

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abso

lute

24.9

510

>10.

.10.

.