EURO-ASIAN COOPERATION OF NATIONAL METROLOGICAL INSTITUTIONS (COOMET)

Transcription

1 ЕВРО-АЗИАТСКОЕ СОТРУДНИЧЕСТВО ГОСУДАРСТВЕННЫХ МЕТРОЛОГИЧЕСКИХ УЧРЕЖДЕНИЙ (KOOMET) EURO-ASIAN COOPERATION OF NATIONAL METROLOGICAL INSTITUTIONS (COOMET) Federal State Unitary Enterprise «Russian Metrological Institute of Technical Physics and Radio Engineering», FSUE «VNIIFTRI» Republican Unitary Enterprise «Belorussian State Institute of Metrology», E «BelGIM» State Enterprise «Scientific-Research Institute for Metrology of Measurement and Control Systems», DP NDI «Systema» COOMET Project No. 66//13 TECHNICAL REPORT OF SUPPLEMENTARY COMPARISON «The comparison of national standards of the sound pressure unit in air through calibration of working standard microphones» COOMET.AUV.A-S Final Report Working group: FSUE «VNIIFTRI» (Russia) pilot laboratory Contact person: Alexey Nikolaenko tel: fax: akustika@vniiftri.ru E «BelGIM» (Belarus) Contact person: Valentina Pozdeeva tel: fax: pozdeeva@belgim.by DP NDI «Systema» (Ukraine) Contact person: Alexander Kosterov tel: fax: kosterov@dndi-systema.lviv.ua 017

2 CONTENTS Introduction Comparison participants Travelling transfer standard Measuring procedure Calibration procedures and equipment used by comparison participants Investigation of the temporal stability of the transer standard Measurement results submitted by the comparison participants Review of comparison results Determination of the reference value of the supplementary comparison and calculation of deviation from the reference value Calculation of the standard uncertainty of measurements and uncertainty of the reference value Evaluation of consistency of comparison results Conclusion... 1 References... 1 APPENDIX А. Technical protocol of the comparison.. APPENDIX B. Information about comparison participants. 6 APPENDIX C. Schedule of calibration 7 APPENDIX D. Information provided by the National Metrological Institutes participating in the comparison... 8

3 INTRODUCTION This Report was prepared based on the overall results of the electrostatic sensitivity level of working reference microphones conducted during a supplementary comparison of national standards of the sound pressure unit in air COOMET.AUV.A-S «Comparison of national standards of the sound pressure unit in air through calibration of inch and half-inch measurement microphones» (COOMET project No. 66//13) The electrostatic method for calibration of measurement microphones is widely used when calibrating working measurement microphones due to its simplicity: it is much less difficult to implement relative to acoustic methods and does not require any complex equipment to be used. It is not restricted by the maximum frequency value of a microphone and may be the only one to provide necessary responses for evaluation the microphone`s sensitivity. Although this method has quite a large measurement uncertainty, it can be accurate enough for most practical applications. Measurement results obtained by this method at the National Metrological Institutes (NMIs) members of COOMET are generally traceable to the standards of the International System of Units (SI), and particularly to the reference value (KCRV) of СIPM Key Comparisons (CIPM KC) though national primary standards. That shall provide for their metrological comparability and formally they are the basis for submission of their relevant CMCs measurement and calibration capabilities for publication in the database of KCDB of the International Bureau of Weights and Measures (BIPM). At the same time, a direct comparison of the results of microphone calibration performed by NMIs can substantially increase the metrological reliability of this measurement method and thus ensure their metrological compatibility *. The decision to conduct a supplementary comparison of national standards of the sound pressure unite in air thought calibration of working reference microphones by the comparison method as shown in IEC and electrostatic actuator method as shown in IEC according to the COOMET project No. 66//13 was taken at the 8 th meeting of the Technical Committee 1. COOMET ТC, held from 10 to 11 September of 013 in Slovak Institute of Metrology (SMU), Bratislava. The decision to conduct a new supplementary comparison of COOMET was a result of the change in the composition of the national standards of the sound pressure unit of NMIs participants, particularly the acquisition of 971 BelGIM`s microphone calibration system, and the modernization of VNIIFTRI and DP NDI «Systema» references. The purpose of this supplementary comparison was the confirmation of Measurement and Calibration Capabilities (CMC) of NMIs comparison participants which provide service category No ,.1.1, 3.1.1, according to the Classification of Services «Acoustics, Ultrasound, Vibration» [1]. The objective of the comparison was to determine the electrostatic sensitivity level of WS1 and WS working reference microphones and evaluate the consistency of results. It was decided to compare the standards using the radial scheme by calibrating WS1 and WS working reference microphones, which are compliant to IEC [], at a frequency of 50 Hz according to IEC [3] and at 1/3 octave band frequencies over the range from 0 Hz to 0 khz in accordance with the requirements of IEC [4] and as specified in the Technical Protocol (Appendix А). It was also decided that VNIIFTRI would act as a pilot laboratory. To evaluate the stability of the transfer standard during the period of comparison, the microphones were calibrated: at the pilot laboratory prior to calibration, between calibrations and after the calibration at the last laboratory of NMIs participant of the comparison. *) terms «metrological comparability» and «metrological compatibility» are given in accordance with.4.6 и.4.7 of the International Vocabulary of Metrology. Saint-Petersburg

4 1. COMPARISON PARTICIPANTS The following National Metrological Institutes (NMIs), registered at BIPM site under COOMET.AUV.A-S, took part in this supplementary comparison: Federal State Unitary Enterprise «Russian Metrological Institute of Technical Physics and Radio Engineering» (FSUE «VNIIFTRI»), Russian Federation (); Republican Unitary Enterprise «Belorussian State Institute of Metrology», E «BelGIM». Belarus (); State Enterprise «Scientific-Research Institute for Metrology of Measurement and Control Systems» (DP NDI «System»), Ukraine (). The more detailed information on the participants is given in Appendix B.. TRAVELLING TRANSFER STANDARD For the comparison, a set of two WS1P and one Bruel & Kjaer WSP microphones satisfying the requirements of IEC [] (Type 4144 with Serial No and and Type 419 with Serial No that are owned by BelGIM were chosen. Microphones were transferred in the original packing as hand-carried items in passenger trains. Abrupt changes in temperature or shocks that could affect sensitivity of microphones were not allowed. Sudden effects caused by sound calibrators, pistonphones or by drying microphones were not also permitted. Each time the microphones had been calibrated at the laboratory of each participant, they were returned to VNIIFTRI. Thus, the stability of the microphones was traced and the results obtained by different laboratories remained comparable even if there were certain changes in their characteristics. The schedule of calibrations performed by NMIs is performed in Appendix C. 3. MEASURING PROCEDURE Each laboratory determined an open-circuit pressure sensitivity level (in db re: 1V/Pa) of each microphone at a reference frequency of 50 Hz according to the requirements of IEC [3] and the frequency response of each microphone using an electrostatic actuator (actuator frequency response of the microphone) according to the requirements IEC [4] at the nominal frequencies of the 1/3 octave band over the range from 0 Hz to 0 khz for the microphone Type WSP. The results of sensitivity level measurements obtained at a reference frequency and according to the requirements IEC [3], from all participants except for BelGIM are traceable to the KCRV through respective primary standards and thus, they are considered as statically independent. The results obtained by BelGIM are traceable through the primary standards of VNIIFTRI, i.e. they are correlated with the results obtained by the latter. When determining the actuator frequency response of the microphone, Bruel & Kjaer electrostatic actuator Type 003 (for WS1P microphones) and Type 0033 (for WSP microphones) were used. The constant bias voltage for the actuator was 800 V. The calibration results are performed for reference environmental conditions according to the standard IEC []. 4

5 Sensitivity level, db re 1V/Pa 4. CALIBRATION PROCEDURES AND EQUIPMENT USED COMPARISON PARTICIPANTS Calibration procedures and equipment used by the NMIs that have taken part in the comparison are shown in the APPENDIX D. 5. INVESTIGATION OF THE TEMPORAL STABILITY OF THE TRANSER STANDARD Measurement results of the open-circuit pressure sensitivity level (in db re: 1V/Pa) of microphones of the transfer standard obtained by VNIIFTRI with the purpose of evaluating their temporal stability are presented in Table 1. Table 1 Measurement results of the open-circuit pressure sensitivity level (in db re: 1V/Pa) of the transfer standard microphones at a reference frequency 51, Hz obtained at VNIIFTRI Microphone type and number 1 st step from to (before BelGIM) Number of a calibration step at VNIIFTRI nd step from 5.08 to (after BelGIM ) 3 rd step from to (after DP NDI «Systema») Maximum change of sensitivity level 4144 No ,155-7,170-7,14 0, No ,571-6,577-6,568 0, No ,903-37,894-37,866 0,037 Each value showed in Table 1, is averaged over 5 observations. A graphical representation of the dependence in sensitivity level of microphones of the transfer standard during the comparison is shown in Tables 1, and Figure 1 Changes in sensitivity levels of the microphone Type 4144 No at a frequency 51, Hz during the comparison with an expanded uncertainty measurement and during the calibration at VNIIFTRI. The calibration steps are numbered in accordance with Table 1 Step 3 5

6 Sensitivity level, db re 1V/Pa Sensitivity level, db re 1V/Pa Figure Changes in sensitivity levels of the microphone Type 4144 No at a frequency 51, Hz during the comparison with an expanded uncertainty measurement and during the calibration at VNIIFTRI. The calibration steps are numbered in accordance with Table 1 Step Step Figure 3 Changes in microphone sensitivity levels of the microphone Type 419 No at a frequency 51, Hz during the comparison with an expanded uncertainty measurement and VNIIFTRI calibration. The calibration steps are numbered in accordance with Table 1 From the Table 1 and Figures 1 to 3 it is evident, that, the maximum sensitivity level changes of microphones Type 4144 No and No lie within 0,08 and 0,009 db respectively, and the microphone Type 419 No lie within 0,037 db. These charges are much lower than an expanded uncertainty values when calibrating in VNIIFTRI and equal to 0,06 db. Thus, the microphones shall be considered quite stable. 6

7 6. MEASUREMENT RESULTS SUBMITTED THE COMPARISON PARTICIPANTS 6.1 Open-circuit pressure sensitivity levels (in db re: 1V/Pa) of microphones of the transfer standard at a reference frequency of 51, Hz, corrected for reference conditions and their total standard and expanded uncertainties are given in Tables and 3 respectively. Table Pressure sensitivity levels of microphones at a reference frequency 51, Hz Microphone type and number Sensitivity level M, db rel. 1 V/Pa M 50, 1 M 50, M 50, No ,14-7,16-7, No ,58-6,57-6, No ,89-37,90-37,87 Table 3 Total standard u c and expanded U uncertainties level measurements at a reference frequency 51, Hz Microphone type Total standard u c and expended U uncertainty, db * u c (M 50, 1 ) U(M 50, 1 ) u c (M 50, ) U(M 50, ) u c (M 50, 3 ) U(M 50, 3 ) WS1 (4144) 0,04 0,08 0,03 0,06 0,035 0,07 WS (419) 0,04 0,08 0,03 0,06 0,05 0,10 *) the uncertainty values are corrected according to the budget. 6. Actuator frequency responses of microphones of the transfer standard and their expanded uncertainties submitted by the comparison participants are given in Tables 4, 5 and 6. 7

8 Table 4 Actuator frequency response R a of the microphone Type 4144 No and its expanded uncertainty U(R a ), db of a reference value at a frequency 51, Hz Frequency, Hz Comparison participants R a1 U(R a1 ) R a U(R a ) R a3 U(R a3 ) 19,95 0,19 0,14 0,16 0,11 0,19 0,15 5,1 0,16 0,14 0,13 0,11 0,15 0,14 31,6 0,1 0,1 0,11 0,11 0,1 0,13 39,81 0,10 0,1 0,09 0,11 0,10 0,1 50,1 0,08 0,1 0,07 0,11 0,08 0,11 63,10 0,07 0,1 0,06 0,11 0,07 0,11 79,43 0,05 0,1 0,05 0,11 0,05 0,10 100,0 0,04 0,1 0,03 0,10 0,04 0,10 15,9 0,0 0,10 0,0 0,10 0,03 0,10 158,5 0,0 0,10 0,01 0,10 0,0 0,10 199,5 0,01 0,10 0,00 0,10 0,01 0,10 51, 0,00 0,00 0,00 0,00 0,00 0,00 316, -0,01 0,10-0,01 0,10 0,00 0,10 398,1-0,01 0,10-0,01 0,10-0,01 0,10 501, -0,01 0,10-0,01 0,10 0,00 0,10 631,0-0,01 0,10-0,01 0,10 0,00 0,10 794,3 0,00 0,10 0,00 0,10 0,01 0, ,0 0,0 0,10 0,0 0,10 0,03 0,10 158,9 0,05 0,10 0,05 0,10 0,06 0, ,9 0,11 0,10 0,11 0,10 0,1 0, ,3 0,19 0,10 0,0 0,10 0,1 0,10 511,9 0,31 0,1 0,33 0,11 0,35 0,11 316,3 0,51 0,1 0,53 0,11 0,56 0,1 3981,1 0,75 0,14 0,8 0,1 0,85 0, ,9 0,9 0,14 1,0 0,14 1,03 0, ,6 0,50 0,14 0,61 0,16 0,60 0,0 7943,3-1,19 0,15-1,10 0,1-1,05 0, ,0-4, 0,18-4,3 0, -4,0 0,30 8

9 Table 5 Actuator frequency response R a of the microphone Type 4144 No and its expanded uncertainty U(R a ), db of a reference value at a frequency 51, Hz Frequency, Hz Comparison participants R a1 U(R a1 ) R a U(R a ) R a3 U(R a3 ) 19,95 0,18 0,14 0,15 0,11 0,1 0,15 5,1 0,16 0,14 0,13 0,11 0,18 0,14 31,6 0,13 0,1 0,11 0,11 0,14 0,13 39,81 0,10 0,1 0,09 0,11 0,11 0,1 50,1 0,08 0,1 0,07 0,11 0,09 0,11 63,10 0,07 0,1 0,06 0,11 0,07 0,11 79,43 0,05 0,1 0,04 0,11 0,06 0,10 100,0 0,04 0,1 0,03 0,10 0,04 0,10 15,9 0,0 0,10 0,0 0,10 0,03 0,10 158,5 0,01 0,10 0,01 0,10 0,0 0,10 199,5 0,01 0,10 0,01 0,10 0,01 0,10 51, 0,00 0,00 0,00 0,00 0,00 0,00 316, -0,01 0,10-0,01 0,10 0,00 0,10 398,1-0,01 0,10-0,01 0,10-0,01 0,10 501, -0,01 0,10-0,01 0,10-0,01 0,10 631,0-0,01 0,10-0,01 0,10-0,01 0,10 794,3 0,00 0,10 0,00 0,10 0,00 0, ,0 0,01 0,10 0,0 0,10 0,0 0,10 158,9 0,04 0,10 0,05 0,10 0,05 0, ,9 0,08 0,10 0,10 0,10 0,09 0, ,3 0,15 0,10 0,17 0,10 0,17 0,10 511,9 0,5 0,1 0,8 0,11 0,9 0,11 316,3 0,4 0,1 0,45 0,11 0,47 0,1 3981,1 0,59 0,14 0,65 0,1 0,67 0, ,9 0,64 0,14 0,7 0,14 0,7 0, ,6 0,0 0,14 0,13 0,16 0,1 0,0 7943,3-1,76 0,15-1,68 0,1-1,63 0, ,0-4,80 0,18-4,76 0, -4,70 0,30 9

10 Table 6 Actuator frequency response R a of the microphone Type 419 No and its expanded uncertainty U(R a ), db of a reference value at a frequency 51, Hz Frequency, Hz Comparison participants R a1 U(R a1 ) R a U(R a ) R a3 U(R a3 ) 19,95 0,06 0,14 0,05 0,11 0,16 0,15 5,1 0,07 0,14 0,05 0,11 0,14 0,14 31,6 0,06 0,1 0,04 0,11 0,1 0,1 39,81 0,04 0,1 0,04 0,11 0,10 0,11 50,1 0,04 0,1 0,04 0,11 0,08 0,10 63,10 0,03 0,1 0,0 0,11 0,07 0,10 79,43 0,0 0,1 0,0 0,11 0,06 0,10 100,0 0,0 0,1 0,01 0,10 0,04 0,10 15,9 0,0 0,10 0,01 0,10 0,03 0,10 158,5 0,01 0,10 0,00 0,10 0,0 0,10 199,5 0,01 0,10 0,00 0,10 0,01 0,10 51, 0,00 0,00 0,00 0,00 0,00 0,00 316, -0,01 0,10-0,01 0,10 0,00 0,10 398,1-0,01 0,10-0,01 0,10-0,01 0,10 501, -0,01 0,10-0,0 0,10-0,01 0,10 631,0-0,0 0,10-0,0 0,10-0,01 0,10 794,3-0,0 0,10-0,0 0,10-0,01 0, ,0-0,0 0,10-0,0 0,10-0,01 0,10 158,9-0,0 0,10-0,0 0,10-0,01 0, ,9-0,0 0,10-0,0 0,10 0,00 0, ,3-0,0 0,10-0,0 0,10 0,00 0,11 511,9-0,01 0,1-0,01 0,11 0,01 0,1 316,3 0,01 0,1 0,01 0,11 0,03 0, ,1 0,04 0,14 0,04 0,1 0,04 0, ,9 0,08 0,14 0,09 0,14 0,07 0,0 6309,6 0,13 0,14 0,16 0,16 0,1 0,5 7943,3 0,1 0,15 0,6 0,1 0,0 0, ,0 0,18 0,18 0,3 0, 0,19 0, ,3-0,07 0,0 0,0 0,3-0,13 0, ,9-0,34 0,5-0,30 0,4-0,48 0, ,6-1,5 0,30-1,15 0,3-1,59 1,00 10

11 7. REVIEW OF COMPARISON RESULTS 7.1 Determination of the reference value of the supplementary comparison and calculation of deviation from the reference value To improve the metrological reliability in the evaluation of the consistency of the results of comparison the reference value M a,ref on electrostatic sensitivity level and its uncertainty u(m a,ref ) in accordance with the COOMET Recommendation R/GM/19:008 [5] was calculated for each microphone at a frequencies of the 1/3 octave band based on the data of two NMIs: VNIIFTRI and DP NDI «Systema» that had previously taken part in key comparisons using primary methods with their LS1 and LS microphones, and their CMCs of which were published in the International Bureau of Weights and Measures (BIPM) KCDB. The reference value of the supplementary comparisons of the electrostatic sensitivity level for each frequency was calculated by the equation: 3 M a, i i uс ( M a, i 3 ) M a, ref, (1) 1 u ( M ) i с a, i where M a,i is the electrostatic sensitivity level for each frequency of the microphone with total standard uncertainty u c (M a,i ) of its measurement (the Formula 4); M a, i M 50, i Ra, i, () where M 50,i is the pressure sensitivity level of the microphone at a reference frequency 51, Hz of the i-th comparison participant; R a,i is the actuator frequency response of the microphone of the i-th participant. Deviation of the electrostatic sensitivity level from the reference value at each frequency of the i-th participant was calculated by the equation: M M, (3) M a, i a, i a, ref where M a,ref is the reference value of the electrostatic sensitivity level at each frequency. The calculation results are given in Tables 7, 8 and 9, and are shown in the form of graphs in Figures 4, 5 and 6. Actuator frequency response R a,i were derived from Tables 4, 5 and 6, the pressure sensitivity level values at a reference frequency M i from Table. The comparison of arithmetic mean deviation of the electrostatic sensitivity level measurement results M a for two microphones of the same type WS1P (4144) from the reference value at the selected frequencies of 0 Hz, 50 Hz and 8 khz for all comparison participants are presented in Figure 7, and the microphone Type WSP (419) at frequencies of 0 Hz, 50 Hz, 10 khz and 0 khz are in Figure 8. 11

12 Deviation, db Table 7 The electrostatic sensitivity level M a (in db re: 1V/Pa) of the microphone Type 4144 No , its reference value M a,ref and deviation δm a from its reference value Frequency, Hz Comparison participants R a1 M a1 δm a1 R a M a δm a R a3 M a3 δm a3 19,95 0,19-6,95 0,03 0,16-7,00-0,0 0,19-6,94 0,04-6,98 5,1 0,16-6,98 0,03 0,13-7,03-0,0 0,15-6,98 0,03-7,01 31,6 0,1-7,0 0,01 0,11-7,05-0,0 0,1-7,01 0,0-7,03 39,81 0,10-7,04 0,01 0,09-7,07-0,0 0,10-7,03 0,0-7,05 50,1 0,08-7,06 0,01 0,07-7,09-0,0 0,08-7,05 0,0-7,07 63,10 0,07-7,07 0,01 0,06-7,10-0,0 0,07-7,06 0,0-7,08 79,43 0,05-7,09 0,00 0,05-7,11-0,0 0,05-7,08 0,01-7,09 100,0 0,04-7,10 0,01 0,03-7,13-0,0 0,04-7,09 0,0-7,11 15,9 0,0-7,1 0,00 0,0-7,14-0,0 0,03-7,10 0,0-7,1 158,5 0,0-7,1 0,01 0,01-7,15-0,0 0,0-7,11 0,0-7,13 199,5 0,01-7,13 0,01 0,00-7,16-0,0 0,01-7,1 0,0-7,14 51, 0,00-7,14 0,01 0,00-7,16-0,01 0,00-7,13 0,0-7,15 316, -0,01-7,15 0,00-0,01-7,17-0,0 0,00-7,13 0,0-7,15 398,1-0,01-7,15 0,01-0,01-7,17-0,01-0,01-7,14 0,0-7,16 501, -0,01-7,15 0,00-0,01-7,17-0,0 0,00-7,13 0,0-7,15 631,0-0,01-7,15 0,00-0,01-7,17-0,0 0,00-7,13 0,0-7,15 794,3 0,00-7,14 0,00 0,00-7,16-0,0 0,01-7,1 0,0-7, ,0 0,0-7,1 0,00 0,0-7,14-0,0 0,03-7,10 0,0-7,1 158,9 0,05-7,09 0,00 0,05-7,11-0,0 0,06-7,07 0,0-7, ,9 0,11-7,03 0,00 0,11-7,05-0,0 0,1-7,01 0,0-7, ,3 0,19-6,95-0,01 0,0-6,96-0,0 0,1-6,9 0,0-6,94 511,9 0,31-6,83-0,0 0,33-6,83-0,0 0,35-6,78 0,03-6,81 316,3 0,51-6,63-0,03 0,53-6,63-0,03 0,56-6,57 0,03-6, ,1 0,75-6,39-0,08 0,8-6,34-0,03 0,85-6,8 0,03-6, ,9 0,9-6, -0,10 1,0-6,14-0,0 1,03-6,10 0,0-6,1 6309,6 0,50-6,64-0,10 0,61-6,55-0,01 0,60-6,53 0,01-6, ,3-1,19-8,33-0,10-1,10-8,6-0,03-1,05-8,18 0,05-8, ,0-4, -31,36 0,01-4,3-31,39-0,0-4,0-31,33 0,04-31,37 М 50-7,14-7,16-7,13 M a,ref ±U ±U ±U Frequency, Hz Figure 4 Deviation δm a (M a,ref was calculated by (two) participants and ) and an expanded uncertainty of the electrostatic sensitivity level measurement of the microphone Type 4144 No

13 Deviation, db Table 8 Electrostatic sensitivity level M a (in db re: 1V/Pa) of the microphone Type 4144 No , its reference value M a,ref and deviation δm a from the reference value Frequency, Hz Comparison participants R a1 M a1 δm a1 R a M a δm a R a3 M a3 δm a3 19,95 0,18-6,40-0,01 0,15-6,4-0,03 0,1-6,34 0,05-6,39 5,1 0,16-6,4-0,01 0,13-6,44-0,03 0,18-6,37 0,04-6,41 31,6 0,13-6,45-0,01 0,11-6,46-0,0 0,14-6,41 0,03-6,44 39,81 0,10-6,48-0,0 0,09-6,48-0,0 0,11-6,44 0,0-6,46 50,1 0,08-6,50-0,0 0,07-6,50-0,0 0,09-6,46 0,0-6,48 63,10 0,07-6,51-0,01 0,06-6,51-0,01 0,07-6,48 0,0-6,50 79,43 0,05-6,53-0,0 0,04-6,53-0,0 0,06-6,49 0,0-6,51 100,0 0,04-6,54-0,01 0,03-6,54-0,01 0,04-6,51 0,0-6,53 15,9 0,0-6,56-0,0 0,0-6,55-0,01 0,03-6,5 0,0-6,54 158,5 0,01-6,57-0,0 0,01-6,56-0,01 0,0-6,53 0,0-6,55 199,5 0,01-6,57-0,0 0,01-6,56-0,01 0,01-6,54 0,01-6,55 51, 0,00-6,58-0,0 0,00-6,57-0,01 0,00-6,55 0,01-6,56 316, -0,01-6,59-0,0-0,01-6,58-0,01 0,00-6,55 0,0-6,57 398,1-0,01-6,59-0,0-0,01-6,58-0,01-0,01-6,56 0,01-6,57 501, -0,01-6,59-0,0-0,01-6,58-0,01-0,01-6,56 0,01-6,57 631,0-0,01-6,59-0,0-0,01-6,58-0,01-0,01-6,56 0,01-6,57 794,3 0,00-6,58-0,0 0,00-6,57-0,01 0,00-6,55 0,01-6, ,0 0,01-6,57-0,03 0,0-6,55-0,01 0,0-6,53 0,01-6,54 158,9 0,04-6,54-0,03 0,05-6,5-0,01 0,05-6,50 0,01-6, ,9 0,08-6,50-0,03 0,10-6,47 0,00 0,09-6,46 0,01-6, ,3 0,15-6,43-0,04 0,17-6,40-0,01 0,17-6,38 0,01-6,39 511,9 0,5-6,33-0,05 0,8-6,9-0,01 0,9-6,6 0,0-6,8 316,3 0,4-6,16-0,06 0,45-6,1-0,0 0,47-6,08 0,0-6, ,1 0,59-5,99-0,09 0,65-5,9-0,0 0,67-5,88 0,0-5, ,9 0,64-5,94-0,10 0,7-5,85-0,01 0,7-5,83 0,01-5, ,6 0,0-6,56-0,1 0,13-6,44 0,00 0,1-6,43 0,01-6, ,3-1,76-8,34-0,1-1,68-8,5-0,03-1,63-8,18 0,04-8, 10000,0-4,80-31,38-0,08-4,76-31,33-0,03-4,70-31,5 0,05-31,30 М 50-6,58-6,57-6,55 M a,ref ±U ±U ±U Frequency, Hz Figure 5 Deviation δm a (M a,ref was calculated by (two) participants and ) and an expanded uncertainty of the electrostatic sensitivity level measurement of the microphone Type 4144 No

14 Deviation, db Table 9 Electrostatic sensitivity level M a (in db re: 1V/Pa) of the microphone Type 419 No , its reference value M a,ref and deviation δm a from the reference value Frequency, Hz Comparison participants R a1 M a1 δm a1 R a M a δm a R a3 M a3 δm a3 19,95 0,06-37,83-0,03 0,05-37,85-0,05 0,16-37,71 0,09-37,80 5,1 0,07-37,8-0,01 0,05-37,85-0,04 0,14-37,73 0,08-37,81 31,6 0,06-37,83-0,01 0,04-37,86-0,04 0,1-37,75 0,07-37,8 39,81 0,04-37,85-0,03 0,04-37,86-0,04 0,10-37,77 0,05-37,8 50,1 0,04-37,85-0,0 0,04-37,86-0,03 0,08-37,79 0,04-37,83 63,10 0,03-37,86-0,0 0,0-37,88-0,04 0,07-37,80 0,04-37,84 79,43 0,0-37,87-0,0 0,0-37,88-0,03 0,06-37,81 0,04-37,85 100,0 0,0-37,87 0,00 0,01-37,89-0,0 0,04-37,83 0,04-37,87 15,9 0,0-37,87 0,00 0,01-37,89-0,0 0,03-37,84 0,03-37,87 158,5 0,01-37,88 0,00 0,00-37,90-0,0 0,0-37,85 0,03-37,88 199,5 0,01-37,88 0,00 0,00-37,90-0,0 0,01-37,86 0,0-37,88 51, 0,00-37,89 0,00 0,00-37,90-0,01 0,00-37,87 0,0-37,89 316, -0,01-37,90-0,01-0,01-37,91-0,0 0,00-37,87 0,0-37,89 398,1-0,01-37,90 0,00-0,01-37,91-0,01-0,01-37,88 0,0-37,90 501, -0,01-37,90 0,00-0,0-37,9-0,0-0,01-37,88 0,0-37,90 631,0-0,0-37,91-0,01-0,0-37,9-0,0-0,01-37,88 0,0-37,90 794,3-0,0-37,91-0,01-0,0-37,9-0,0-0,01-37,88 0,0-37, ,0-0,0-37,91-0,01-0,0-37,9-0,0-0,01-37,88 0,0-37,90 158,9-0,0-37,91-0,01-0,0-37,9-0,0-0,01-37,88 0,0-37, ,9-0,0-37,91-0,01-0,0-37,9-0,0 0,00-37,87 0,03-37, ,3-0,0-37,91-0,01-0,0-37,9-0,0 0,00-37,87 0,03-37,90 511,9-0,01-37,90-0,01-0,01-37,91-0,0 0,01-37,86 0,03-37,89 316,3 0,01-37,88-0,01 0,01-37,89-0,0 0,03-37,84 0,03-37, ,1 0,04-37,85 0,00 0,04-37,86-0,01 0,04-37,83 0,0-37, ,9 0,08-37,81 0,00 0,09-37,81 0,00 0,07-37,80 0,01-37, ,6 0,13-37,76-0,0 0,16-37,74 0,00 0,1-37,75-0,01-37, ,3 0,1-37,68-0,03 0,6-37,64 0,01 0,0-37,67-0,0-37, ,0 0,18-37,71-0,04 0,3-37,67 0,00 0,19-37,68-0,01-37, ,3-0,07-37,96-0,05 0,0-37,88 0,03-0,13-38,00-0,09-37, ,9-0,34-38,3-0,01-0,30-38,0 0,0-0,48-38,35-0,13-38, 1995,6-1,5-39,14-0,05-1,15-39,05 0,04-1,59-39,46-0,37-39,09 М 50-37,89-37,90-37,87 M a,ref ±U ±U ±U Frequency, Hz Figure 6 Deviation δm a (M a,ref was calculated by (two) participants and ) and an expanded uncertainty of the electrostatic sensitivity level measurement of the microphone Type 419 No

15 Deviation, db Deviation, db Deviation, db Deviation, db Deviation, db Deviation, db Deviation, db 0.50 Frequency 0 Hz 0.50 Frequency 50 Hz 0.50 Frequency 8 khz Figure 7 The comparison of deviations of the electrostatic sensitivity level of the microphone Type WS1P (4144) from the reference value at frequencies of 0 Hz, 50 Hz and 8 khz with the image of the expanded uncertainties measurements of the comparison participants Frequency 0 Hz 0.50 Frequency 50 Hz Frequency 10 khz 0.80 Frequency 0 khz Figure 8 The comparison of deviations of the electrostatic sensitivity level of the microphone Type WSP (419) from the reference value at frequencies of 0 Hz, 50 Hz and 8 khz with the image of the expanded uncertainties measurements of the comparison participants

16 7. Calculation of the standard uncertainty of measurements and uncertainty of the reference value The standard total measurement uncertainty of the electrostatic sensitivity level was calculated by the equation: u c( M a, i c 50, i с a, i ) u ( M ) u ( R ), (4) where u c (M 50,i ) is the standard total measurement uncertainty of the sensitivity level of the microphone М 50,i at a reference frequency 51, Hz of the i-th participant (see Table 3); u c (R a,i ) is the standard total measurement uncertainties of the actuator frequency response R a,i of the microphones, obtained by the division of expanded uncertainties U(R a,i ), given in Tables 4, 5 and 6 by the coverage factor k = ; The standard uncertainty u(m a,ref ) of the reference value of the supplementary comparison for two NMIs (VNIIFTRI and DP NDI «Systema») according to of the Recommendation of COOMET R/GM/19:008 [5] for each microphones at a frequency of the 1/3 octave band was calculated by the equation: 1 u ( M ). (5) a, ref 3 1 uc ( M a, i ) i The standard total measurement uncertainty u c (M a,i ) of the electrostatic sensitivity level and the standard uncertainty of the reference value u(m a,ref ) of the microphones Types WS1P and WSP of the i-th comparison participant are given in Tables 10 and 11. Table 10 The standard total measurement uncertainty of the electrostatic sensitivity level and the standard uncertainty of the reference value of the supplementary comparison for the microphone Type WS1P (4144), db Frequency, Hz Comparison participants u c (R a1 ) u c (M a1 ) u c (R a ) u c (M a ) u c (R a3 ) u c (M a3 ) u(m a,ref ) 19,95 0,07 0,08 0,06 0,06 0,08 0,08 0,05 5,1 0,07 0,08 0,06 0,06 0,07 0,08 0,05 31,6 0,06 0,07 0,06 0,06 0,07 0,07 0,05 39,81 0,06 0,07 0,06 0,06 0,06 0,07 0,05 50,1 0,06 0,07 0,06 0,06 0,06 0,07 0,05 63,10 0,06 0,07 0,06 0,06 0,06 0,07 0,05 79,43 0,06 0,07 0,06 0,06 0,05 0,06 0,04 100,0 0,06 0,07 0,05 0,06 0,05 0,06 0,04 15,9 0,05 0,06 0,05 0,06 0,05 0,06 0,04 158,5 0,05 0,06 0,05 0,06 0,05 0,06 0,04 199,5 0,05 0,06 0,05 0,06 0,05 0,06 0,04 51, 0,00 0,04 0,00 0,03 0,00 0,04 0,0 316, 0,05 0,06 0,05 0,06 0,05 0,06 0,04 398,1 0,05 0,06 0,05 0,06 0,05 0,06 0,04 501, 0,05 0,06 0,05 0,06 0,05 0,06 0,04 631,0 0,05 0,06 0,05 0,06 0,05 0,06 0,04 794,3 0,05 0,06 0,05 0,06 0,05 0,06 0, ,0 0,05 0,06 0,05 0,06 0,05 0,06 0,04 158,9 0,05 0,06 0,05 0,06 0,05 0,06 0, ,9 0,05 0,06 0,05 0,06 0,05 0,06 0, ,3 0,05 0,06 0,05 0,06 0,05 0,06 0,04 511,9 0,06 0,07 0,06 0,06 0,06 0,07 0,05 316,3 0,06 0,07 0,06 0,06 0,06 0,07 0, ,1 0,07 0,08 0,06 0,07 0,07 0,07 0, ,9 0,07 0,08 0,07 0,08 0,08 0,08 0, ,6 0,07 0,08 0,08 0,09 0,10 0,11 0, ,3 0,08 0,09 0,11 0,11 0,13 0,13 0, ,0 0,09 0,10 0,11 0,11 0,15 0,15 0,09 u c (M 50 ) 0,04 0,03 0,035 16

17 Table 11 The standard total measurement uncertainty of the electrostatic sensitivity level and the standard uncertainty of the reference value of the supplementary comparison for the microphone Type WSP (419), db Frequency, Hz Comparison participants u c (R a1 ) u c (M a1 ) u c (R a ) u c (M a ) u c (R a3 ) u c (M a3 ) u(m a,ref ) 19,95 0,07 0,08 0,06 0,06 0,08 0,09 0,05 5,1 0,07 0,08 0,06 0,06 0,07 0,09 0,05 31,6 0,06 0,07 0,06 0,06 0,06 0,08 0,05 39,81 0,06 0,07 0,06 0,06 0,06 0,07 0,05 50,1 0,06 0,07 0,06 0,06 0,05 0,07 0,05 63,10 0,06 0,07 0,06 0,06 0,05 0,07 0,05 79,43 0,06 0,07 0,06 0,06 0,05 0,07 0,05 100,0 0,06 0,07 0,05 0,06 0,05 0,07 0,04 15,9 0,05 0,06 0,05 0,06 0,05 0,07 0,04 158,5 0,05 0,06 0,05 0,06 0,05 0,07 0,04 199,5 0,05 0,06 0,05 0,06 0,05 0,07 0,04 51, 0,00 0,04 0,00 0,03 0,00 0,05 0,03 316, 0,05 0,06 0,05 0,06 0,05 0,07 0,04 398,1 0,05 0,06 0,05 0,06 0,05 0,07 0,04 501, 0,05 0,06 0,05 0,06 0,05 0,07 0,04 631,0 0,05 0,06 0,05 0,06 0,05 0,07 0,04 794,3 0,05 0,06 0,05 0,06 0,05 0,07 0, ,0 0,05 0,06 0,05 0,06 0,05 0,07 0,04 158,9 0,05 0,06 0,05 0,06 0,05 0,07 0, ,9 0,05 0,06 0,05 0,06 0,06 0,07 0, ,3 0,05 0,06 0,05 0,06 0,06 0,07 0,05 511,9 0,06 0,07 0,06 0,06 0,06 0,08 0,05 316,3 0,06 0,07 0,06 0,06 0,07 0,08 0, ,1 0,07 0,08 0,06 0,07 0,08 0,09 0, ,9 0,07 0,08 0,07 0,08 0,10 0,11 0, ,6 0,07 0,08 0,08 0,09 0,13 0,13 0, ,3 0,08 0,09 0,11 0,11 0,16 0,16 0, ,0 0,09 0,10 0,11 0,11 0,18 0,18 0, ,3 0,10 0,11 0,1 0,1 0,3 0,3 0, ,9 0,13 0,13 0,1 0,1 0,33 0,33 0,1 1995,6 0,15 0,16 0,16 0,16 0,50 0,50 0,15 u c (M 50 ) 0,04 0,03 0,05 17

18 7.3 Evaluation of consistency of comparison results The consistency of the data comparisons is evaluated in accordance with the item 6 of the Recommendation of COOMET R/GM/19:008 [5] (these comparisons are to the second type) using the consistency criterion E, which can be represented by the formula: M a, i Ei 1, (6) u ( M ) u ( M ) cov( M, M ) c a, i a, ref 1 where δm a,i is determined by the formula: 1 n M a, i j M 1 a, i, j, (7) n is the arithmetic mean deviation δm a,i of the electrostatic sensitivity level measurement M a, i results for n-count uniform microphones of one type (two microphones 4144 of Type WS1P (see Tables 7 and 8) and one microphone 419 of Type WSP (see Table 9). The deviation δm a,i,j is determined by the formula 3 for j-th microphone. The consistency criterion E i is defined for WS1P and WSP microphones; u c (M a,i ) is the standard total uncertainty of the electrostatic sensitivity level measurement of the microphones of the i-th participant; u(m a,ref ) is the standard uncertainty of the reference value of the supplementary comparison; cov(m 1, M ref ) is the covariance of the measurement results of NMIs participant (BelGIM) and the reference value of the supplementary comparison due to unit size taken from one of the reference NMIs (VNIIFTRI). In accordance with [5], total standard uncertainty dispersion from the reference NMI was taken as a covariance and determined by the formula: cov( M1, M ref ) u0 ( M 50), (8) u 0 (M 50 ) = u(m 50,LS1P ) = 0,015 db is used at calculation covariance for microphones of Type WS1P at frequency 50 Hz, u 0 (M 50 ) = u(m 50,LSP ) = 0,05 db for microphone of Type WSP. At calculating consistency criterion E i of the electrostatic sensitivity measurement level in total frequency range the same value cov(m 1, M ref ) = 0,0003 for microphones of Type WS1P, cov(m 1, M ref ) = 0,00063 for microphone of Type WSP is used. The NMIs participants VNIIFTRI and DP NDI «Systema» reproduce unit by independent primary method, cov(m, M ref ) = 0 и cov(m 3, M ref ) = 0. The results of consistency criterion calculations E of the sensitivity level measurement for WS1P and WSP microphones are given in Tables 1 and 13 respectively and also presented as graphs in Figures 9 and 10. ref 18

19 Criterion E Table 1 Evaluation of consistency of comparison results for the microphone Type WS1P, db Comparison participants Frequency, Hz δm a1 u c (M a1 ) E 1 δm a u c (M a ) E δm a3 u c (M a3 ) E 3 u(m a,ref ) 19,95 0,01 0,08 0,05-0,03 0,06 0,16 0,04 0,08 0,3 0,05 5,1 0,01 0,08 0,06-0,0 0,06 0,15 0,04 0,08 0,0 0,05 31,6 0,00 0,07 0,01-0,0 0,06 0,1 0,03 0,07 0,15 0,05 39,81 0,00 0,07 0,0-0,0 0,06 0,11 0,0 0,07 0,13 0,05 50,1 0,00 0,07 0,0-0,0 0,06 0,1 0,0 0,07 0,13 0,05 63,10 0,00 0,07 0,01-0,0 0,06 0,11 0,0 0,07 0,11 0,05 79,43-0,01 0,07 0,05-0,0 0,06 0,1 0,0 0,06 0,11 0,04 100,0 0,00 0,07 0,01-0,0 0,06 0,1 0,0 0,06 0,1 0,04 15,9-0,01 0,06 0,08-0,0 0,06 0,1 0,0 0,06 0,1 0,04 158,5-0,01 0,06 0,04-0,0 0,06 0,1 0,0 0,06 0,1 0,04 199,5 0,00 0,06 0,03-0,01 0,06 0,10 0,0 0,06 0,11 0,04 51, -0,01 0,04 0,06-0,01 0,03 0,14 0,01 0,04 0,17 0,0 316, -0,01 0,06 0,08-0,0 0,06 0,1 0,0 0,06 0,1 0,04 398,1-0,01 0,06 0,05-0,01 0,06 0,08 0,01 0,06 0,09 0,04 501, -0,01 0,06 0,06-0,01 0,06 0,10 0,0 0,06 0,11 0,04 631,0-0,01 0,06 0,06-0,01 0,06 0,10 0,0 0,06 0,11 0,04 794,3-0,01 0,06 0,06-0,01 0,06 0,10 0,0 0,06 0,11 0, ,0-0,01 0,06 0,09-0,01 0,06 0,10 0,0 0,06 0,11 0,04 158,9-0,01 0,06 0,09-0,01 0,06 0,10 0,0 0,06 0,11 0, ,9-0,0 0,06 0,11-0,01 0,06 0,08 0,01 0,06 0,09 0, ,3-0,0 0,06 0,16-0,01 0,06 0,10 0,0 0,06 0,11 0,04 511,9-0,04 0,07 0,3-0,0 0,06 0,1 0,0 0,07 0,13 0,05 316,3-0,04 0,07 0,5-0,0 0,06 0,14 0,03 0,07 0,16 0, ,1-0,08 0,08 0,44-0,0 0,07 0,14 0,03 0,07 0,15 0, ,9-0,10 0,08 0,50-0,01 0,08 0,07 0,0 0,08 0,08 0, ,6-0,11 0,08 0,53-0,01 0,09 0,03 0,01 0,11 0,04 0, ,3-0,11 0,09 0,47-0,03 0,11 0,11 0,04 0,13 0,14 0, ,0-0,03 0,10 0,13-0,0 0,11 0,08 0,05 0,15 0,13 0, Frequency, Hz Figure 9 Evaluation of consistency of comparison results for the microphone Type WS1P (4144): due to the consistency criterion E 19

20 Criterion E Table 13 Evaluation of consistency of comparison results for the microphone Type WSP, db Comparison participants Frequency, Hz δm a1 u c (M a1 ) E 1 δm a u c (M a ) E δm a3 u c (M a3 ) E 3 u(m a,ref ) 19,95-0,03 0,08 0,13-0,05 0,06 0,8 0,09 0,09 0,45 0,05 5,1-0,01 0,08 0,06-0,04 0,06 0,6 0,08 0,09 0,39 0,05 31,6-0,01 0,07 0,08-0,04 0,06 0,7 0,07 0,08 0,36 0,05 39,81-0,03 0,07 0,16-0,04 0,06 0,4 0,05 0,07 0,30 0,05 50,1-0,0 0,07 0,1-0,03 0,06 0,0 0,04 0,07 0,3 0,05 63,10-0,0 0,07 0,09-0,04 0,06 0, 0,04 0,07 0,6 0,05 79,43-0,0 0,07 0,1-0,03 0,06 0,0 0,04 0,07 0,3 0,05 100,0 0,00 0,07 0,03-0,0 0,06 0,16 0,04 0,07 0,1 0,04 15,9 0,00 0,06 0,00-0,0 0,06 0,14 0,03 0,07 0,18 0,04 158,5 0,00 0,06 0,00-0,0 0,06 0,14 0,03 0,07 0,18 0,04 199,5 0,00 0,06 0,0-0,0 0,06 0,11 0,0 0,07 0,14 0,04 51, 0,00 0,04 0,0-0,01 0,03 0,10 0,0 0,05 0,0 0,03 316, -0,01 0,06 0,04-0,0 0,06 0,11 0,0 0,07 0,14 0,04 398,1 0,00 0,06 0,01-0,01 0,06 0,08 0,0 0,07 0,11 0,04 501, 0,00 0,06 0,0-0,0 0,06 0,11 0,0 0,07 0,14 0,04 631,0-0,01 0,06 0,04-0,0 0,06 0,11 0,0 0,07 0,14 0,04 794,3-0,01 0,06 0,04-0,0 0,06 0,11 0,0 0,07 0,14 0, ,0-0,01 0,06 0,04-0,0 0,06 0,11 0,0 0,07 0,14 0,04 158,9-0,01 0,06 0,04-0,0 0,06 0,11 0,0 0,07 0,14 0, ,9-0,01 0,06 0,06-0,0 0,06 0,13 0,03 0,07 0,18 0, ,3-0,01 0,06 0,06-0,0 0,06 0,13 0,03 0,07 0,18 0,05 511,9-0,01 0,07 0,05-0,0 0,06 0,1 0,03 0,08 0,17 0,05 316,3-0,01 0,07 0,05-0,0 0,06 0,1 0,03 0,08 0,16 0, ,1 0,00 0,08 0,00-0,01 0,07 0,06 0,0 0,09 0,09 0, ,9 0,00 0,08 0,0 0,00 0,08 0,0 0,01 0,11 0,03 0, ,6-0,0 0,08 0,08 0,00 0,09 0,01-0,01 0,13 0,0 0, ,3-0,03 0,09 0,1 0,01 0,11 0,03-0,0 0,16 0,06 0, ,0-0,04 0,10 0,14 0,00 0,11 0,01-0,01 0,18 0,0 0, ,3-0,05 0,11 0,18 0,03 0,1 0,08-0,09 0,3 0,19 0, ,9-0,01 0,13 0,03 0,0 0,1 0,05-0,13 0,33 0,19 0,1 1995,6-0,05 0,16 0,1 0,04 0,16 0,09-0,37 0,50 0,35 0, Frequency, Hz Figure 10 Evaluation of consistency of comparison results for the microphone Type WSP (419): due to the consistency criterion E 0

21 8. CONCLUSION 1. The frequency response stability for the microphones of the transfer standard, estimated by the change of their pressure sensitivity level at a frequency 51, Hz during the measurements is satisfactory. The maximum change in sensitivity levels for the microphones of the transfer standard does not exceed the expanded uncertainty of the measurement in calibration in the VNIIFTRI pilot laboratory. Thus, the microphones can be considered quite stable.. Analysis of the results of the measurements of the electrostatic sensitivity level by the comparison participants shows that their results are consistent across the range of frequencies from 0 Hz to 10 khz for inch microphones Type WS1P (4144) and from 0 Hz to 0 khz for half-inch microphones Type WSP (419). For all NMIs comparison participants the consistency criterion E is less than one..1 The maximum consistency criterion value of the electrostatic sensitivity measurement level for inch microphones Type WS1P on the secondary standard VET (VNIIFTRI) is 0,16 at a frequency 19,95 Hz, and for half-inch microphones Type WSP is 0,8 at a frequency Hz.. The maximum consistency criterion value of the electrostatic sensitivity measurement level for inch microphones Type WS1P on the microphone calibration system Type 971 from the National standard NS RB (BelGIM) is 0,53 at a frequency 6309,6 Hz, and for half-inch microphones Type WSP is 0,18 at a frequency 1589,3 Hz..3 The maximum consistency criterion value of the electrostatic sensitivity measurement level for inch microphones Type WS1P on the secondary standard VETU (DP NDI «Systema») is 0,3 at a frequency 19,95 Hz, and for half-inch microphones Type WSP is 0,45 at a frequency 19,95 Hz. Thus, the obtained results confirm the uncertainties of the electrostatic sensitivity measurement level for inch and half-inch working standard microphones Types WS1P and WSP respectively. REFERENCES 1. Classification of Services «Acoustics, Ultrasound, Vibration» Version.0 (October 00, updated in October 004). IEC Measurement microphones Part 4: Specifications for working standard microphones 3. IEC Measurement microphones Part 5: Methods for pressure calibration of working standard microphones by comparison 4. IEC Measurement microphones Part 6: Electrostatic actuators for determination of frequency response 5. COOMET Recommendation R/GM/19:008. Guideline on COOMET supplementary comparison evaluation 1