The two‐microphone sound intensity method is potentially a valuable tool for noise source identification, sound power determination, and for other measurements (e.g., transmission loss) that are based on sound intensity measurements. An essential ingredient in an accurate sound intensity measurement is the accurate measurement of the phase between the two microphones. Because the phase is generally small, on the order of a few degrees, the microphones must either be “phase matched,” or a phase calibration procedure must be used. This paper outlines the design and test procedures for using a plane‐wave tube to perform a microphone phase calibration with an uncertainty of less than approximately 0.2 deg. The phase calibration procedure is illustrated for a pair of condenser microphones and for a pair of miniature crystal microphones typically used in hearing aids.