Abstract:

Sound calibrators are designed to generate known sound-pressure levels at specified frequencies. Performances of calibrators are usually verified by accredited acoustical test laboratories. According to the latest standard revision [IEC 60942, Ed. 2, Sound Calibrator], the level of ambient noise reaching the microphone during testing of the calibrator shall be at least 30 dB lower than the measured sound-pressure level for class 0 and 1 calibrators, and at least 25 dB lower than the measured sound-pressure level for class 2 calibrators. For calibrators, high-ambient noise will affect the uncertainty of the measurement, and this is particularly severe when the calibrator is operating at a relatively low sound-pressure level, such as 74 dB. In this paper, methods to reduce the effect of ambient noise on calibrators are presented. The uncertainties of the measurement associated with the methods are estimated. The measured sound-pressure levels based on the new methods are compared with those measured in an anechoic chamber using the traditional method.