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| The Impact to the Low-frequency Reciprocity Calibration Caused by Heat Conduction and Sound Leakage in the Coupler |
| QIU Jian-min1, HE Long-biao2, XU Huan2, ZHONG Bo2, NIU Feng2 |
1.Zhejiang Province Institute of Metrology, Hangzhou, Zhejiang 310013, China;
2.National Institute of Metrology, Beijing 100013, China |
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Abstract The effect of heat conduction and sound leakage in the coupler on the low-frequency reciprocity calibration was discussed. The theoretical calculations and the experiments with different lengths of the couplers were implemented to find the rules. First by the principle of the reciprocity calibration and the frequency response characteristics of the condenser microphones in low frequency was described. The sound pressure sensitivity gradually increased as the frequency decreased, and the heat conduction correction factor in the coupled system by the excited microphone - coupler - received microphone become smaller when the lengths of the couplers turned to longer, and the uncertainty components become smaller . Different lengths of the couplers were used to study the impaction of the sound leakage and the optimization program was explored. The experimental results showed that, with 10mm and 15mm couplers the leakage had smaller impaction and the sensitivity had high reproducibility. At the same time, the experimental results conformed the low frequency response characteristics of the condenser microphones in low frequencies.
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［3］ IEC 61094-2 Ed.2: Electroacoustics-Measurement microphones-Part 2: Primary method for the pressure calibration of laboratory standard microphones by the reciprocity technique. Commission Electrotechnique Internationale International Electrotechnical Commission［S］. 2009. |
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2013, Vol. 34 
