Bilateral comparison on pressure calibration of LS1P and LS2P microphones

Final Report, 17 June 2004

The bilateral comparison on primary pressure calibration of LS1P and LS2aP microphones was carried out between DPLA and BNM-LNE. Two microphones from BNM-LNE have been used as transfer standards. Calibrations were performed in 20 Hz to 10 kHz range for LS1P microphones and in 31.5 Hz to 20 kHz range for LS2aP microphones.

The results for LS2aP 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.(ua² ub²)½ both in dB.

Frequency
(Hz)
Expanded uncertainties in dB (k=2)BNM-LNE - DPLA
Degree of equivalence in dB
DPLA (Ua)BNM-LNE (Ub)DifferenceExp. Unc.
31.50.0800.045-0.0040.092
630.0400.0350.0010.053
1250.0300.0350.0040.046
2500.0300.0350.0030.046
5000.0300.0350.0040.046
10000.0300.0350.0020.046
12500.0300.0350.0040.046
16000.0300.0350.0020.046
20000.0300.0350.0040.046
25000.0300.0350.0050.046
31500.0300.0350.0050.046
40000.0300.0350.0020.046
50000.0300.0400.0050.050
63000.0300.0400.0130.050
80000.0300.0500.0000.058
100000.0300.0650.0080.072
125000.0400.0850.0000.094
160000.0500.1200.0170.130
200000.0800.200-0.0080.215

The results for LS1P microphone are following:

Frequency
(Hz)
Expanded uncertainties in dB (k=2)BNM-LNE - DPLA
Degree of equivalence in dB
DPLA (Ua)BNM-LNE (Ub)DifferenceExp. Unc.
200.0600.035-0.0110.069
250.0500.035-0.0090.061
31.50.0500.030-0.0080.058
630.0300.030-0.0040.042
1250.0250.0300.0000.039
2500.0250.0300.0010.039
5000.0250.0300.0040.039
10000.0250.0300.0050.039
12500.0250.0300.0030.039
16000.0250.030-0.0020.039
20000.0250.0300.0010.039
25000.0300.0350.0040.046
31500.0300.0400.0020.050
40000.0300.045-0.0100.054
50000.0500.055-0.0090.074
63000.0500.075-0.0230.090
80000.0500.0900.0370.103
100000.0800.150-0.0740.170

Degree of equivalence between both partners shows that BNM-LNE 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.


Proposal

Bilateral comparison between BNM-LNE and DPLA following the Euromet AUV.A-K1

Procedure.

BNM-LNE is now equipped with a new reciprocity setup allowing computer driven measurements.
The method for determination of the microphone parameters (equivalent volume, resonance frequency and loss factor) are totally new.
The uncertainty budget was reviewed.

So, this bilateral comparison is necessary to validate these recent improvements.

Subjects
Acoustics, Ultrasound and Vibration (AUV)
Coordinator
Jean-Noël Durocher, LNE (France)
Coordinating Institute
LNE (France)
Participating Partners
Further Partners
DPLA