Abstract | A sound calibrator contains a stable sound source that can be coupled to the microphone of a measuring instrument. This allows the calibration of an entire measurement system prior to a measurement. The calibration of the measurement system is so important that many noise regulations specify the requirement of calibration. The sound calibrator itself needs to be calibrated routinely traceable to national standards. The International Standard IEC 60942:2003, Electroacoustics - Sound calibrators, specifies performance requirements for the sound pressure level generated by a sound calibrator, especially the short-term level fluctuation of sound pressure. The aim of this paper is to evaluate several methods proposed for the measurement of fluctuation in the sound pressure level generated by the sound calibrator. Specifically, this paper focuses on the sound level meter method, the analyzer method (using either a FFT analyzer or a set of 1/n octave band filters), and the time capture method. The analysis is emphasized on the key points for implementing IEC 60942:2003. The time capture method implemented at National Research Council Canada has a measurement uncertainty of 0.016 dB, which is better than the maximum permitted expanded uncertainty of measurement for short-term level fluctuation specified in IEC 60942:2003. |
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