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 2004-05-17
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) | Difference | Exp. Unc. | |
| 20 | 0.1 | 0.08 | -0.065 | 0.128 |
| 31.5 | 0.08 | 0.05 | -0.056 | 0.094 |
| 63 | 0.04 | 0.04 | -0.049 | 0.057 |
| 125 | 0.03 | 0.04 | -0.045 | 0.05 |
| 250 | 0.03 | 0.03 | -0.041 | 0.042 |
| 500 | 0.03 | 0.03 | -0.039 | 0.042 |
| 1000 | 0.03 | 0.03 | -0.038 | 0.042 |
| 1250 | 0.03 | 0.03 | -0.038 | 0.042 |
| 1600 | 0.03 | 0.03 | -0.036 | 0.042 |
| 2000 | 0.03 | 0.03 | -0.037 | 0.042 |
| 2500 | 0.03 | 0.03 | -0.034 | 0.042 |
| 3150 | 0.03 | 0.03 | -0.033 | 0.042 |
| 4000 | 0.03 | 0.03 | -0.035 | 0.042 |
| 5000 | 0.03 | 0.03 | -0.031 | 0.042 |
| 6300 | 0.03 | 0.03 | -0.032 | 0.042 |
| 8000 | 0.03 | 0.03 | -0.033 | 0.042 |
| 10000 | 0.03 | 0.03 | -0.02 | 0.042 |
| 12500 | 0.04 | 0.04 | -0.023 | 0.057 |
| 16000 | 0.05 | 0.05 | 0.004 | 0.071 |
| 20000 | 0.08 | 0.07 | -0.042 | 0.106 |
| 25000 | 0.14 | 0.14 | -0.098 | 0.198 |
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) | Difference | Exp. Unc. | |
| 20 | 0.06 | 0.08 | -0.023 | 0.1 |
| 25 | 0.05 | 0.05 | -0.022 | 0.071 |
| 31.5 | 0.05 | 0.05 | -0.02 | 0.071 |
| 63 | 0.03 | 0.05 | -0.016 | 0.058 |
| 125 | 0.025 | 0.03 | -0.015 | 0.039 |
| 250 | 0.025 | 0.03 | -0.011 | 0.039 |
| 500 | 0.025 | 0.03 | -0.009 | 0.039 |
| 1000 | 0.025 | 0.03 | -0.008 | 0.039 |
| 1250 | 0.025 | 0.03 | -0.007 | 0.039 |
| 1600 | 0.025 | 0.03 | -0.012 | 0.039 |
| 2000 | 0.025 | 0.03 | -0.013 | 0.039 |
| 2500 | 0.03 | 0.03 | -0.013 | 0.042 |
| 3150 | 0.03 | 0.03 | -0.016 | 0.042 |
| 4000 | 0.05 | 0.03 | -0.031 | 0.058 |
| 5000 | 0.05 | 0.05 | -0.026 | 0.071 |
| 6300 | 0.05 | 0.05 | -0.035 | 0.071 |
| 8000 | 0.05 | 0.07 | 0.059 | 0.086 |
| 10000 | 0.08 | 0.08 | 0.044 | 0.113 |
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.