Calibration of pressure-velocity probes using a progressive plane wave reference field and comparison with nominal calibration filters

Abstract

A procedure for calibrating pressure-velocity (p-v) sound intensity probes using a progressive plane wave as reference field is presented here. The procedure has been checked for a microelectromechanical system technology-based Microflown(®) match-size probe by comparing the calibration results with the nominal correction curves available from the manufacturer. The reference field was generated along a wave guide by means of a dual cone loudspeaker supplying acoustic energy in the range 20 Hz-20 kHz through an impedance adaptor. Different from the current in-field procedures, the one proposed here allows the calibration of probes under test to be executed at once up to 10 kHz without any change in the experimental setup. After a detailed review of the general principles of calibration, the procedure has been finalized with three main stages: (a) determination of the full coherence calibration bandwidth of the probe, (b) comparison calibration of the probe built-in pressure microphone over the full coherence frequency range, and (c) relative calibration of the velocity sensor over the calibrated pressure one. Calibration results for the probe under test have been best fitted against the calibration filters modeled by the manufacturer and the direct comparison of the obtained data with the factory ones has been reported.

Measurement of complex acoustic intensity in an acoustic waveguide

“…However, at very low or high frequencies when the sound field is either strongly active or reactive, the measurement accuracy strongly depends on the accuracy of the phase calibration 22 . Furthermore, the majority of the Microflown calibration reports published so far in the literature are based on measuring intensity in one direction only 19,22,23 .…”

“…Furthermore, the majority of the Microflown calibration reports published so far in the literature are based on measuring intensity in one direction only 19,22,23 . The only calibration investigation available for a 'p-u' probe measuring pressure and velocities in three orthogonal directions simultaneously is provided by the manufacturer 17 .…”

Precision device for measuring the three dimensional spectra of complex intensity

“…The general calibration process as introduced in [2], can be summarized by means of two calibration functions K and Γ defined in the frequency domain by the two equations:…”

Wide band pressure and velocity (p-v) tympanometry with calibrated sound intensity micro-probes

“…Results of figure 3 were obtained with a commercially available sound intensity micro-probe which was previously calibrated using a progressive plane wave (PPW) reference field as completely accounted in [3]. The calibration procedure is summarized below for completeness.…”

“…It is worth to point out that at present, tympanometric signals are obtained only with a pressure microphone, so no direct measurement of the immittance function of the ear is accomplished: this process would require, in fact, the acquisition of the concatenated air particle velocity signal in addition to the acoustic pressure one. The possibility of using well calibrated p-v sound intensity microprobes [3] has been recently demonstrated by two of the authors of the present paper [5], in connection with recent developments of wide band excitation tympanometry and the concept of Energy Absorbance (EA) [4]. The p-v approach to audiometric measures is possible thanks to the development of MEMS sensors, whose size makes them optimal to be used in such particular applications; it can be safely stated that this approach is the key to discover an entire new horizon to energetic audiometry.…”