Higher Order Ambisonics (HOA) is a flexible approach for representing and rendering 3D sound fields. Nevertheless, lack of effective microphone systems limited its use until recently. As a result of authors’ previous work on the theory and design of spherical microphone arrays, a 4th order HOA microphone has been built, measured and used for natural recording. The present paper first discusses theoretical aspects and physical limitations proper to discrete, relatively small arrays (spatial aliasing, low-frequency estimation). Then it focuses on the objective validation of such microphones. HOA directivities reconstructed from simulated and measured 3D responses are compared to the expected spherical harmonics. Criteria like spatial correlation help characterizing the encoding artifacts due to the model limitations and the prototype imperfections. Impacts on localisation criteria are evaluated.
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