Calibration and digital equalization of the intensimetric probe Microflown

The Microflown probe is equipped with a microphone and 3 velocity sensors. To calibrate them, it is generated an acoustic field with known properties, deducting their sensitivity from the response of the reference microphone. For low frequency range, the relationship between the pressure inside the spherical source and particles velocity in front of the speaker is known; from this, velocity is obtained at a certain distance from the sphere. Therefore the digital filters are calculated to correct the sensors’ responses: their sum with the relative phase is equalized with an all-pass filter. The equalization system has an accuracy of 0.1 dB in amplitude and 5° in phase.