Bilateral comparison on primary pressure calibration of LS1P and LS2P microphones.

Project Description

The Spanish National Metrology Institute has improved and developed its facilities with a microphone primary calibration system, which was put into functioning in January 2002. In order to check the capability measurement calibration a bilateral comparison is necessary.The frequency range for LS1P microphones is: 20 Hz to 10 kHz, and for LS2P: 20 Hz to 25 kHz.


Final Report

The bilateral comparison on primary pressure calibration of LS1P and LS2P microphones was carried out between DPLA and CEM. Two microphones from DPLA have been used as transfer standards. Calibrations were performed in 20 Hz to 10 kHz range for LS1P microphones and in 20 Hz to 25 kHz range for LS2P microphones.

The results for LS2P microphone are given in the table below. The table shows the expanded uncertainties (Ua, Ub) as reported by the participants and the degree of equivalence between the two participants is given by a pair of numbers; the difference between the reported calibration results and the associated expanded uncertainty (2÷sqrt(ua^2+ub^2)) both in dB.

Frequency
(Hz)
Expanded
uncertainties in dB
(k=2)
CEM – DPLA
Degree of equivalence
in dB
 DPLA (Ua)CEM (Ub)DifferenceExp. Unc.
200.10.08-0.0650.128
31.50.080.05-0.0560.094
630.040.04-0.0490.057
1250.030.04-0.0450.05
2500.030.03-0.0410.042
5000.030.03-0.0390.042
10000.030.03-0.0380.042
12500.030.03-0.0380.042
16000.030.03-0.0360.042
20000.030.03-0.0370.042
25000.030.03-0.0340.042
31500.030.03-0.0330.042
40000.030.03-0.0350.042
50000.030.03-0.0310.042
63000.030.03-0.0320.042
80000.030.03-0.0330.042
100000.030.03-0.020.042
125000.040.04-0.0230.057
160000.050.050.0040.071
200000.080.07-0.0420.106
250000.140.14-0.0980.198

 

The results for LS1P microphone are following:

Frequency
(Hz)
Expanded
uncertainties in dB
(k=2)
CEM – DPLA
Degree of equivalence
in dB
 DPLA (Ua)CEM (Ub)DifferenceExp. Unc.
200.060.08-0.0230.1
250.050.05-0.0220.071
31.50.050.05-0.020.071
630.030.05-0.0160.058
1250.0250.03-0.0150.039
2500.0250.03-0.0110.039
5000.0250.03-0.0090.039
10000.0250.03-0.0080.039
12500.0250.03-0.0070.039
16000.0250.03-0.0120.039
20000.0250.03-0.0130.039
25000.030.03-0.0130.042
31500.030.03-0.0160.042
40000.050.03-0.0310.058
50000.050.05-0.0260.071
63000.050.05-0.0350.071
80000.050.070.0590.086
100000.080.080.0440.113

 

Degree of equivalence between both partners shows that CEM primary pressure microphones calibration system is in reasonably good agreement with DPLA. The observed differences in the calibration results are all within the expanded uncertainties. The results for LS2 microphones will be substituted by the ongoing key-comparison, EUROMET project 674.

Subjects
Acoustics, Ultrasound and Vibration (AUV)
Coordinator
del Carmen Casal Sobrino, CEM (Spain)
Coordinating Institute
CEM (Spain)
Participating Partners
Further Partners
DPLA