Reciprocity calibration in a plane wave resonator

A non-standard method for the electroacoustic reciprocity calibration of a condenser microphone is theoretically developed and experimentally employed to calibrate a WE640AA laboratory standard microphone. The average experimental calibration so obtained was found to be in absolute agreement with a pressure coupler comparison calibration of the same microphone made at the National Bureau of Standards to within an experimental uncertainty (sigma) of 0.03 dB over the frequency range of 245 to 1470 Hz. using a 70 cm. plane wave resonant cavity, and to within an experimental uncertainty (sigma) of 0.06 dB over the frequency range of 735 to 1470 Hz. using a 23 cm. plane wave resonant cavity. Above 1470 Hz., the difference between the resonant plane wave reciprocity calibrations and the pressure coupler comparison calibration increased linearly with frequency to a maximum of 0.61 dB at 5145 Hz.