iMP presents two novel works on audio processing, work carried out by Barcelona Media:

G. Cengarle, T. Mateos, D. Bonsi, A second order Ambisonic device using velocity transducers Accepted for publication as a regular paper in the Journal of the Audio Engineering Society.

Abstract: The relation between sound pressure gradient and air particle velocity is exploited to obtain second order spherical harmonics of the pressure field via velocity gradients. The existence of anemometric transducers capable of directly measuring the acoustic velocity field might therefore allow the construction of higher order Ambisonics microphones of very small size and accurate polar patterns. This possibility is simulated numerically and tested experimentally employing two Microflown pressure-velocity probes in a face to face configuration, validating the results through the analysis of the second order polar responses measured in anechoic conditions. To conclude, a proposal for the design of a three-dimensional second order device using the minimum number of transducers is presented.

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G. Cengarle, T. Mateos, Comparison of anemometric probe and tetrahedral microphones for sound intensity measurements Presented at the 130th AES Convention, London, May 2011.

Abstract: The measurement of sound intensity requires the acquisition of sound pressure and acoustic velocity in a coincident position. Various transducers topologies can be used to measure the acoustic velocity directly or indirectly. In this paper, three transducers are compared: a pressure-velocity anemometric probe and two tetrahedral B-Format microphones from different manufacturers. The comparison has been carried out in different fields, ranging from anechoic to diffuse, reverberant field conditions. The analysis and comparison is based on intensimetric quantities such as the radiation index and the sound intensity vector. Strengths and limitations of the various approaches are reported, to suggest the preferred application for each transducer.