The results of an interlaboratory comparison on microphone calibration involving five National Metrology Institutes (NMIs) are presented. The Institute for National Measurement Standards (INMS—Canada), was the pilot laboratory that provided the data analysis for this investigation. The final results presented here were discussed and agreed upon by all participants. The maximum rms deviation for the two LS1P laboratory standard microphones measured by the above participants is 0.037 dB, which may be considered as the key comparison reference value.