Calculation of uncertainty in calibration of microphones by the pressure reciprocity technique

At the primary level, acoustical measurement standards are realized through calibration of the sensitivity level of Laboratory Standard microphones by the reciprocity technique. The technique is described in International Standard IEC 61094‐2, which allows for various implementations of the measurement method. The pressure sensitivity levels of a set of three microphones are determined from the electrical and acoustical transfer impedances of pairs of the microphones. The transfer impedances in turn depend on the design and performance of the measurement apparatus, the dimensions and acoustical properties of the microphones and the cavity that acts as an acoustical coupler between the microphones, and the prevailing environmental conditions. The uncertainty in the pressure sensitivity level depends on the uncertainties in these input quantities and on how the sensitivity level varies with changes in the input quantities. The ISO/IEC Guide Express: 1995 Guide to the Expression of Uncertainties in Measureme...