The basic theory of measurement uncertainty as found in national and international acoustical standards is reviewed. Random error, bias error, confidence interval, coverage factor, and expanded uncertainty are defined. The concept of acceptance intervals applied to tolerance limits for outgoing quality control and incoming inspection is presented. Calculation of the maximum permitted uncertainty is detailed and its application in the development of an uncertainty budget for a given measurement is shown. Example uncertainty budgets are developed for a number of common electroacoustic measurements including loudspeakers, microphones, telephones, earphones, and hearing aids. Use of the uncertainty budget as a diagnostic tool to find problems in the specification of various components in a measurement chain is demonstrated on the ANSI S3.22-2014 hearing aid standard. Lastly, the uncertainty is calculated for a measurement of random noise and its dependence on bandwidth and averaging time is examined.

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