Calibration of a cardioid microphone for improving accuracy of normal impedance measurement in a tube

This paper presents a method for obtaining the complex amplitudes of both the sound pressure and the particle velocity of a cardioid microphone. These values are used as calibration values in a new technique for measuring the impedance of materials using a combination of two cardioid microphones placed in a tube. The previous technique, which utilized a single cardioid microphone placed in a tube, required two separate measurements to be taken - one with the microphone facing the specimen and one with the microphone facing away. This new method provides a more efficient approach to impedance measurement.