The importance of automatic calibration for sound level meter (SLM) is described and the problems of existing calibration systems are analysed at the beginning of this paper. Then a novel automatic calibration system based on image recognition technology for frequency weighting functions of SLM is presented. Firstly, the system can realise automatic calibration of sound fields which produce expected standard sound pressure both in anechoic chamber and active coupler. Through the image recognition technology, it can obtain the measured value of SLM automatically. This unique feature solves the problem that many automatic calibration systems can't deal with SLMs which don't have electrical output interface so that it enlarges the application scope of our system. In addition, the system can generate final reports automatically according to the calibration results. The experiment results show that our system has the features of high-efficiency, easy-operation, and good-universality and it is well competent for routine calibration work for SLM.
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